凡佩带防毒面具进入有毒区作业前，均要对其进行气密性检查。
参考答案：对
下列不宜用阴阳的基本概念来概括的是
A.寒与热
B.上与下
C.动与静
D.邪与正
Which of the following was the only major war during the late eighteenth century().
A.The war in the Middle East.
B.The war in South Africa.
C.The war in Latin America.
D.The war between Britain and France.
