垃圾车每天冲洗（）次，摆放整齐，无强异味，停放于制定地点。
A.1
B.2
C.3
D.4
参考答案：A
In order to keep their trade _____, they would have to buy less goods in the United States. [ ]
A. balanced
B. balancing
C. to balance
D. being balanced
若要除去下列各物质中的杂质，写出所用试剂的化学式
（1）除去MgCl2中混有的少量MgCO3，可选用______溶液；
（2）除去FeCl2中混有的少量Cu2+，可选用______；
（3）除去Fe粉中混有的少量Al粉，可选用______ 溶液．
