The result of a Promise

Father: I promised to buy you a car if you passed your examination, and you have failed. What were you doing last term?父亲：我曾向你许诺，如果你考试及格就给你买俩小汽车，可你却未能做到。你上学期一直在干什么呀？Son: I was learning to drive a car.儿子：我在学开汽车。