—— Is Jack back?—— No but I think he in half an hour.A. come backB. came backC. comes ba

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。