What Is the Main Purpose of Submitting a Concept Paper

What is the main purpose of submitting a Concept Paper (otherwise known as a Letter of Inquiry or a Letter of Intent) to a funding agency?

A) To obtain grant writing assistance from the funding agency
B) For applicants to obtain informal feedback on their project prior to preparing a proposal
C) To gain political leverage or a competitive edge over applicants who do not submit a Concept Paper
D) None of the above