A defendant got into a physical altercation with a third party after the third party insulted his honor. At the defendant's battery trial, the prosecutor called a witness of the altercation, believing he would testify that the defendant was the initial aggressor. The witness behaved in a hostile manner to the prosecutor, refusing to testify that the defendant was the initial aggressor in the altercation at issue. The prosecutor decided to call a second witness to minimize any damage done by the first witness's testimony. This second witness, who was the first witness's sister, testified that in her opinion, her brother was too easily provoked by insults and had poor judgment regarding who should be considered the initial aggressor in a fight. She also testified that just before the trial, her brother had been goaded into a fight similar to the one he had witnessed between the defendant and the third party. The defendant's attorney objects to the sister's testimony. Should the prosecutor be allowed to ask the sister about the witness's fight just before trial? a. Yes, because the credibility of a witness may be attacked by reputation or opinion evidence. b. Yes, because the first witness put his character at issue by testifying. c. No, because the prosecutor cannot impeach his own witness. d. No, because the altercations have no bearing on the first witness's character for untruthfulness