He kept his job as a bus driver.
He【主语】// kept【谓语动词】// his job 【宾语】//as a bus driver.【宾补】
解答:as a bus driver 为介词短语作宾补成分
They kept him as a prisoner.他们把他监禁起来。
That kept him as a student.那使他继续当学生。
You may keep it as a souvenir if you like.如果你愿意,就把它留下来作纪念品。