氯气用于维持（）。
A、水中较低的微生物数
B、在初级污水处理中形成颗粒物质
C、在土壤中形成腐败
D、净化慢速滤器
参考答案：A
看图，用适当的单词完成对话。
1. A: _____ _____ are your black _____ ?
B: They are ten dollars.
2. A: _____ is your brother?
B: He is _____ the tree.
3. A: When is your_____ ?
B: It's October seventh. And today is October seventh.
A: Oh! _____ _____ to you!
B：Thank you.
4. A: What _____ of movies does her grandmother like?
B: She likes Beijing _____.
烈度指的是( )。
A．地震后受震地区地面影响和破坏的强烈程度
B．地震强度大小
C．弯曲突出处和断裂带交叉处
D．地震后地面的最大开裂度
