装饰材料大理石、瓷砖对室内环境产生的主要污染物是( )。
A．甲醛
B．氨
C．氡
D．苯
参考答案：C
The settlement is home to nearly 1,000 people, many of()left their village homes for a better life in the city.
A. whom
B. them
C. which
D. those
行口对口人工呼吸时吹气毕，放开鼻孔是因为
A．防止吹气量过大B．及时引流鼻腔分泌物C．排出呼吸道内气体D．利于肺泡再次扩张E．及时降低腹腔压力
