工班个体粉尘测定中呼吸性粉尘浓度在1个工作班次每个工种先后采集的有效样品数不得少于（）个。
A.7
B.6
C.5
D.4
参考答案：D
—What made her so happy?
—Her parents decided her a new computer.[ ]
A to feel; buy
B. to feel; to buy
C. feel; to buy
D. feel; buy
太平洋型大陆边缘
