Sage Offers to Pay Allison $450 If Allison Will Paint

Multiple Choice

Sage offers to pay Allison $450 if Allison will paint her apartment while she is out of town on vacation for two weeks.Allison makes no promise but tells Sage that she will think about it.While Sage is out of town,Allison paints the apartment.This is best described as a(n) :

A) unilateral contract.
B) quasi contract.
C) implied in fact contract.
D) bilateral contract.