问题补充:
—— Is Jack back?
—— No, but I think he in half an hour.
A. come back
B. came back
C. comes back
D. is coming back
答案:
A. come back
B. came back
C. comes back
D. is coming back
解析:考查动词时态。句意:杰克回来了吗?没有,但我认为他在半小时内将会回来的。根据in half an hour得知是将来时,come可以用正在进行时表将来,故选D项。