Greatly_________ as the leading scientist,he was asked to give lectures in many countries.

A．respecting

B．respects

C．respected

D．to respect

清扫过程中如发现煤粉仓内残留的煤粉有自燃现象时，清扫人员应立即退到仓外，将煤粉仓严密封闭用（）灭火。

A.蒸气

B.蒸气或二氧化碳

C.蒸气或干砂灭火器

D.泡沫灭火器