Little Bob is too shy to speak if he is not spoken to
问题描述：
Little Bob is too shy to speak if he is not spoken to
Little Bob is too shy to speak _____ ______to
答
填上：unless spoken .
原句的意思是：小Bob太怕羞了,如果没有人跟他说话,他都不会主动说的.
unless是“除非”.本来完整的同义句应该是
Little Bob is too shy to speak unless he is spoken to.小Bob太害羞了,除非有人跟他说话,否则他是不会主动开口的.
unless引导的从句中：
1、主语和主句的主语一样,都是指Bob
2、从句谓语是be动词
满足以上两个条件,可以省略主语和be动词,变成Little Bob is too shy to speak unless spoken to.