单项选择题
Corey in a desperate need to get to the airport decides to take his neighbor Tanner's help.Tanner agrees to help and drives Corey to the airport.Upon arrival at the airport, Corey promises to pay Tanner $25 for the gas fill.Corey's promise falls under which of the following contracts().
A、illegal consideration
B、illusory promise
C、preexisting duty
D、past consideration
A.Tanner
B.Upon
C.Corey's
D.
A、illegal