It is written clearly in the requirements that all passengers check onto board t

It is written clearly in the requirements that all passengers _______ check onto board thirty minutes before the plane takes off.

　 A．may 　 B．can C．will　 　 D．shall

试题答案

D

shall作为情态动词，用于第二，三人称中表示许诺，警告，命令的意思。