Question

【题目】Simon's mom won't let him go out unless(除非) he promises _________back before 10 o'clock tonight.

A. to beB. beC. isD. was

Answer 1

【答案】A

【解析】

句意：Simon的妈妈不让他出去，除非他答应在晚上10点之前回来。to be动词不定式；be是，动词原形；is是，用于主语为单数时；was是is的过去式。空前动词promises意为“承诺，答应”，常用于句型promise to do sth.答应做某事，故应选A。