Answer:
A. Letter of Inquiry
Step-by-step explanation:
Because an LOI (Letter of Inquiry) is to generate interest and a desire to hear more in a full proposal for example "I want to research and know about the process of marketing. Therefore, I request you to grant me one day's permission from your company and inquire about the marketing process. I would be thankful if you give me a chance to conduct the research. Please let me know your answer" which is asking for a person to respond to ask someone a "personal" question or in your case as the senator for their opinion.
Hope this helped!