Question

--- Some schools have used smart uniforms. I wonder        .

--- They can tell parents where their children are.

A.who invented them B.what they are used for C.when students wear them

Answer

B

【解析】

句意：-有的学校已经运用了智能的校服。我想知道它们被用来做什么。-他们能告诉父母他们的孩子在哪儿。who invented them谁发明了他们；what they are used for他们用来干什么；when students wear them学生们什么时候穿他们。根据下面的答语They can tell parents where their children are可知，题目中问的是智能校服的用途，故应选B。