Stay awake! You should know that it to sleep in class.
A. doesn’t permit
B. is not permitted
C. will not be permitted
D. was not permitted
网友回答
A. doesn’t permit
(答案→)B. is not permitted
C. will not be permitted
D. was not permitted
解析：句意：保持清醒，你应该知道在课堂上是不允许睡觉的。这里it是形式主语，to sleep in class是真正的主语，根据Stay awake可知说的现在不能睡觉，所以应该用现在时故选B。