Final answer:
Option D) Ask trusted friends their opinions of your field is the least effective in developing business acumen.
Step-by-step explanation:
The least effective course of action in helping you develop business acumen would be option D) Ask trusted friends their opinions of your field.
While getting opinions from friends can be valuable for personal decisions, it may not provide the objective and professional insights needed to develop business acumen.
Instead, options A) Find an internship in your field, B) Ask a professional in your field to mentor you, and C) Interview experienced people in your field would be more effective in developing business acumen as they provide direct exposure, guidance, and expert knowledge.