There must have been something wrong with the society _______ no one offers to help those who are in trouble.

A．when

B．where

C．which

D．that

下列有关焊炬和割炬在使用中应注意的事项，哪些是正确的？（）

A.点火前，应检查焊、割炬的射吸性能

B.点火前，应检查焊、割炬的气密性

C.点火时，应先开氧气阀门，点燃后立即开乙炔阀门

D.焊、割炬的喷嘴发生堵塞时，应停止操作

E.停用时，应先关乙炔气阀门，后关氧气阀门