发生该情况的原因是

A．失水失钠，引起周围循环衰竭
B．盐分补充不足，使血液中钠、氯浓度降低
C．强烈热辐射引起脑组织充血水肿
D．体温调节功能障碍
E．缺氧所致

All passengers ___ to show their tickets next time.

A．require

B．will require

C．are required

D．are to require