You stepped into the lab with your shoes on? You’re to take them off before you enter it.
A. invited
B. supposed
C. forbidden
D. permitted
网友回答
A. invited
(答案→)B. supposed
C. forbidden
D. permitted
解析：考查动词。be supposed to do应当做某事。根据句意你进实验室之前应当把鞋脱了，选B。