[1] Defendant challenges the sufficiency of the hypothetical question propounded to plaintiff’s expert witness concerning the cause of the separation of the outer wheel from the hub of the Ken-worth tractor. The witness, John C. Jeffries, was tendered and accepted without objection as an expert mechanic, damage analyst, and appraiser. Jeffries personally examined the wheel that separated from the plaintiff’s truck. At trial he described the wheel assembly and the proper mounting technique. Plaintiff’s counsel then submitted the following question to the witness:
“Q. Okay. Now, I’m going to ask you to assume some facts, if you will, please. If you could assume that the jury should find by the evidence and the greater weight that on November *15411th, 1977 (sic), while driving on a highway near Fort Worth, Texas, at a speed of approximately fifty miles an hour, this wheel, the same wheel that has been designated as Plaintiff’s Exhibit A, came off of a 1971 Kenworth tractor then being operated by the plaintiff, David Lee, and that approximately one month earlier than that, Mr. Lee had had this wheel installed by the defendant, Capitol Tire Company, and in the meantime driven some twelve to fourteen thousand miles. Now, based on those facts and on your personal examination of this wheel, do you have an opinion as to what caused this tire and wheel to separate from the hub and come off?
MR. McDaniel: Objection.
COURT: Overruled. EXCEPTION NO. 1
A. Yes, sir, I do.
Q. And what is that opinion?
A. In my opinion, the inner nuts were not properly tightened before the outer wheel was put on, . . .”
After the witness elaborated on the basis of his opinion, defendant moved to strike the testimony essentially on the grounds that the question failed to include any hypothesis with respect to the pre-existing condition of the wheel, ie. defendant’s contention that plaintiff insisted that the tires be mounted despite his knowledge that some of the lug nuts could not be replaced. Defendant objects to the question on the basis of the well-established rule in this State that a hypothetical question omitting facts which go to the very essence of the case may be so incomplete that an expert’s opinion based thereon would be unreliable and objectionable. See State v. Taylor, 290 N.C. 220, 226 S.E. 2d 23 (1976); Dean v. Coach Co., 287 N.C. 515, 215 S.E. 2d 89 (1975). The rule is to prevent the submission of opinions which are based on information clearly insufficient to form the basis of an opinion, not to require a propounded hypothetical question to assume every state of facts which could be found from the evidence. It is permissible in this State to ask an expert for an opinion based upon different combinations of facts. If a party is concerned that omitted facts might elicit a different opinion from the expert, it is incumbent upon him to elicit an opinion based upon a counter-hypothetical question containing other facts which the jury could find from the evidence. See Dean v. Coach Co., *155 supra; Godfrey v. Power Co., 190 N.C. 24, 128 S.E. 485 (1925); State v. Stewart, 156 N.C. 636, 72 S.E. 193 (1911). Similarly, it has been suggested that the better practice is to permit questions which contain less than all facts material to the issue because to require the inclusion of all facts would lead to lengthy, meaningless questions. The safeguards preventing misleading questions include cross-examination (see generally E. Cleary, McCormick on Evidence § 14 (2d ed.)), and the rule disallowing an opinion based on a set of facts clearly insufficient as a basis for an opinion.
It is elementary that a hypothetical question submitted to an expert should include only those facts which a jury could be justified in inferring from the evidence. See generally 1 Stansbury’s N.C. Evidence § 137 (Brandis rev. 1973). Defendant contends that plaintiff’s hypothetical question was fatally defective for failing to include facts relating to (1) how the wheel was initially installed, (2) the previous condition of the wheel assembly, (3) interim use or misuse of the wheel, and (4) the fact that some of the lug nuts may have intentionally been left off. The only evidence in the record prior to the questioning of the witness negated defendant’s contentions that there was preexisting damage to the wheel and that some of the lug nuts were intentionally not replaced. There was no evidence concerning the other facts. Therefore, the plaintiff’s hypothetical question could not properly assume facts not in evidence.
Furthermore, defendant was afforded the opportunity to vigorously cross-examine the expert concerning the basis of his opinion. He questioned the expert with respect to the possibility that the damage may have existed prior to defendant’s mounting of the wheels and that some lugs may not have been replaced at plaintiff’s insistence. This is the proper function of cross-examination and raised weaknesses perceived by defendant to exist in the expert’s opinion testimony.
The objection to the hypothetical question was properly overruled. The factors not included in the question were either facts within the expert’s personal knowledge, and thus not required to be included in the question (see generally 1 Stansbury’s N.C. Evidence § 136 (Brandis rev. 1973)), or were facts as contended by the defendant which were the object of vigorous cross-*156examination. Those facts included in the hypothetical question were supported by plaintiff’s evidence. The expert’s personal knowledge and those facts supplied by the question provided a sufficient foundation for the witness’ opinion testimony. It was incumbent upon defendant’s cross-examination to expose any weakness in that testimony. Defendant’s first assignment of error is overruled.
[2] Defendant excepts to the court’s denial of its motions for a directed verdict and judgment notwithstanding the verdict and assigns error to these rulings. We note initially that the record does not disclose the specific grounds for defendant’s motions for a directed verdict. G.S. 1A-1, Rule 50(a) mandates: “A motion for a directed verdict shall state the specific grounds therefor.” Our Supreme Court has recognized that the requirement is mandatory, although the courts need not enforce the rule infexibly when the grounds for the motion are apparent to the trial court and the parties. Anderson v. Butler, 284 N.C. 723, 202 S.E. 2d 585 (1974); see also Clary v. Board of Education, 286 N.C. 525, 212 S.E. 2d 160 (1975). Defendant subsequently moved for a G.S. 1A-1, Rule 50(b) judgment notwithstanding the verdict following the jury verdict in plaintiff’s favor and did state grounds for the motion. The reviewability of the trial court’s rulings on similar motions was addressed by this Court in Love v. Pressley, 34 N.C. App. 503, 239 S.E. 2d 574 (1977), cert. denied, 294 N.C. 441, 241 S.E. 2d 843 (1978), which is controlling. We quote:
“Upon failure to state specific grounds, an appellant cannot question on appeal the insufficiency of the evidence to support the verdict. Wheeler v. Denton, [9 N.C. App. 167, 175 S.E. 2d 769 (1970)]. The motion for judgment notwithstanding the verdict is technically only a renewal of the motion for a directed verdict made at the close of all the evidence, and thus the movant cannot assert grounds not included in the motion for directed verdict. House of Koscot Development Corp. v. American Line Cosmetics, Inc., 468 F. 2d 64 (5th Cir., 1972).” Love v. Pressley, 34 N.C. App. at 511, 239 S.E. 2d at 580.
Even if we were to infer from the record that defendant’s motion for a directed verdict was based on the insufficiency of the evidence of negligence to go to the jury, defendant is deemed to *157have abandoned that exception by failing to assign this specific ground of error and by failing to make supporting arguments in the brief. See N.C. Rules of Appellate Procedure, Rule 10(c) and Rule 28(a).
Furthermore, we note that defendant did not plead the affirmative defenses of contributory negligence and assumption of the risk as required by G.S. 1A-1, Rule 8(c). Consequently, defendant is not entitled to that defense upon a motion for directed verdict, nor was it entitled to instructions regarding the issues of contributory negligence or assumption of risk.
Defendant further assigns error to the trial court’s summary of the evidence indicating that plaintiff rented a substitute trailer and the instruction concerning damages for loss of use of the trailer, to the court’s failure to charge the jury concerning the expert’s testimony that failure to replace the lug nuts could cause the wheel to come off, and to the denial of defendant’s motion for a new trial. We note initially that defendant’s brief fails to refer to the proper exception numbers in certain instances and refers to the wrong page numbers of the exceptions in every instance. See North Carolina Rules of Appellate Procedure, Rule 28(e) (see also Drafting Committee Note to Subdivision (e) (1977 Cum. Supp.)). This Court will not “fish out” an appellate’s exceptions which are not referred to by the proper printed page number. See e.g., Shepard v. Oil & Fuel Co., 242 N.C. 762, 89 S.E. 2d 464 (1955); Rawls v. Lupton, 193 N.C. 428, 137 S.E. 175 (1927). Thus defendant’s remaining assignments of error are not properly before this Court and need not be considered. Nevertheless, we have reviewed the record and have found no valid reason for disturbing the result reached in the trial court.
No error.
Judges MARTIN (Harry C.) and CARLTON concur.