导致安全壳早期失效的原因
参考答案：
直接安全壳加热、蒸汽爆炸、氢气燃烧和安全壳隔离失效等。
中小跨桥梁实体桥墩的墩帽厚度，不应小于()。
A.0.2m
B.0.3m
C.0.4m
D.0.5m
________ us calmly together, our captain made an announcement__________ we must save essential supplies before the day broke.
A．Calling; that
B．To call; that
C．Calling; which
D．To call; which
