Mostofthetimeweareunawareofwhat

問題詳情：

 Most of the time we are unaware of what ______ in our bodies; usually it is only when we get sick or feel pain that we notice.

A. happen                   B. happens                 C. is happening          D. has happened

【回答】

C

知識點：現在進行時及其被動式

題型：選擇題