The foot-in-the-door method is basically a psychological method where you ask for a small request first, then a bigger one later. So I think it's A, just because the others don't work. B is just straight up asking for a big favor, C is providing you with the "must-do" effect, and D is simply a favor for a favor.
An example would be the great mistakes he's made
Answer:
You're
it doesn't make sense to put "your" there. "You're" is the combination of "You" and "Are" so it would fit.
