问题
选择题
It is written clearly in the requirements that all passengers ______ check onto board 30 minutes before the plane takes off.
A．may
B．can
C．will
D．shall
答案
答案：D
requirements当要求讲，后面的同位语从句that all passengers ______ check onto board 30 minutes before the plane takes off.应该用（should）+do的虚拟语气，