问题
选择题
Please don't stand up in class until you ________.
A．are told
B．will be told
C．are told to
D．will tell
答案
答案：C
题目分析：句意：只到你被叫到才能站起来。Not …until…直到…才…主句是将来时态，从句要用一般现在时态。故排除BD；此句，要用被动语态，故排除D；这里是tell sb to do的被动形式即sb be told to do；这里的to后省略了stand up；但是这里的to不能省略，故选C。
