循环水的含油量指标是多少？
参考答案：
含油量＜5mg/1（炼油厂＜10mg/l﹚
无并发症的麻疹患儿，从出疹日计算，应隔离的天数是（）
A.1天
B.2天
C.3天
D.5天
E.7天
____ is often the case, we can't find the things when we need them. [ ]
A. Which
B. When
C. What
D. As
