--Look! The light in the study is still on.Sorry I forgot it off.AturningBturnC

问题补充：

--Look! The light in the study is still on.

--Sorry, I forgot it off.

Aturning

Bturn

Cturned

Dto turn

答案：

A. turning

B. turn

C. turned

(答案→)D. to turn

解析：考查forget的用法。 Forget to do 意为忘记去干某事 forget doing sth 意为忘记做过了某事本句意为---看，书房里的灯还是亮着的，----对不起，我忘记去关掉它了。