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.
He is captured by a colonel who is son of Don Lupe that was killed by Juvencio. When some men are trampling on his small property he goes out to tell them not to do that when he is captured. He doesn't want to die and he says that he is not a threat to anybody because he is too old then the colonel tells his men to get Juvencio drunk.
