Which of the following is something a lawyer may tell a witness before a trial?

A) What to say in response to a question
B) That the opposing counsel may ask confusing or leading questions
C) That trials are a waste of time
D) All of these choices are correct.

Lawyers often prepare witnesses for trial by advising them that the opposing counsel may ask confusing or leading questions to challenge their testimony or credibility. This is part of witness preparation, aiming to make the witness more comfortable and effective in giving testimony. Telling a witness what to say or suggesting that trials are a waste of time would be unethical and unprofessional.