With an appropriate preposition: (1)My father began to work ____

With an appropriate preposition:
(1)My father began to work ____ a bus driver when he was twenty years old. (2)The teacher is busy ____ teaching.
【正确答案】：asin
【题目解析】：考点点击本题考查介词。要点透析】as作介词时,意为“作为……,以……身份”。 be busy in doing sth.意为“忙于做某事”。