－IsJackinthenextroom?        －Well,it’shardtosay.ButIhe...

問題詳情：

－Is Jack in the next room?

         －Well, it’s hard to say. But I heard him ______ at 5 o’clock.

A. sing               B. to sing        C. sang                    D. singing

【回答】

D

知識點：動詞和動詞短語

題型：選擇題