Final answer:
The primary function of a credible witness in a trial is to give testimony. So, the correct answer is option 2.
Step-by-step explanation:
The primary function of a credible witness in a trial is to give testimony. In a criminal trial, both the prosecution and the defense have the opportunity to present witnesses who can provide testimony related to the case. The witness must be credible, meaning that they are considered trustworthy, unbiased, and well-informed about the matter they are testifying about. Their testimony is subject to cross-examination by the opposing party to test its reliability and credibility.
So, the correct answer is option