Why is D wrong?

@jingjingxiao11111@gmail.com, happy to help! (D) is incorrect because extensive interviewing of witnesses by lawyers on both sides of a case before witnesses appear in court would likely provide opportunity for more leading questions to be introduced. (E) is correct because it would allow the court to review any instance of leading questions that occurred before the courtroom. The passage discusses the prevalence of such earlier questioning in lines 9-17. Does that make sense? Please let us know if you have any other questions!

Why is A incorrect here? I struggled between choosing between A and E, but landed on A?

There is nothing in the passage about needing more time. The issue is that a question can insert details in a memory that were not there. We are never told that time pressure on asking questions is a factor.