'for+Ving' or 'to+Vinfi' or anything else!

I am being made confused.Help me please!Thanks in advance!
Fill in the blank with the most suitable selection:
‘’’‘I stopped at a foodstall …’’’’’
A. for lunch B.to have lunch
C.for having lunch D.All are incorrect
Be my friends!

Assuming that is possible to buy lunch at a “food stall”, my choice would be A.

If it is also possible to eat lunch at a “food stall”, then I suppose B might work, too.

I agree .But why don’t you choose C?