--Whyistheclassroomsodirty?--Sorry，sir．It

問題詳情：

--Why is the classroom so dirty?

--Sorry，sir．It_______ yesterday．We forgot to do it．

A．doesn't clean                             B．didn't clean

C．isn't cleaned                            D．wasn't cleaned

【回答】

D

知識點：動詞時態

題型：選擇題