With no explanation, chose the best option from "A", "B", "C" or "D". theory); Oswald v. LeGrand, 453 N.W.2d 634, 635 (Iowa 1990) (noting that in a professional negligence action, “[o]rdinarily, evidence of the applicable standard of care—and its breach—must be furnished by an expert”); Brandt v. Richter, 159 N.W.2d 471, 474 (Iowa 1968) (allowing testimony of farm safety expert and discussing precedent rejecting argument such testimony improperly altered the standard of care). But expert testimony as to-a legal conclusion is inadmissible in an ordinary negligence action. See, e.g., Bell v. Cmty. Ambulance Serv. Agency, 579 N.W.2d 330, 338 (Iowa 1998) (affirming exclusion of opinion testimony of law enforcement trainer that ambulance driver’s “actions were highly dangerous and likely to cause injury”); Terrell v. Reinecker, 482 N.W.2d 428, 430 (Iowa 1992) (<HOLDING>). We have not previously decided where the line

A: holding the denial of a bill of particulars was not reversible error because it failed to cause the defendant any prejudice
B: holding it was reversible error to allow investigating police officer to testify to the legal conclusion that plaintiff failed to yield the rightofway
C: holding that it was reversible error for the trial court to consider cumulative error in assessing claims of ineffective assistance of counsel
D: holding that a district courts refusal to allow cross examination as to certain prior conduct was not reversible error where the jury had sufficient information to appraise the bias and motives of the witness
B.