火灾分（）四类。
参考答案：
A、B、C、D
Not only I but also he helpful to others. [ ]
A. am
B. is
C. are
D. be
NaOH及KOH应在（）中称量。
A.玻璃器皿
B.试纸
C.滤纸
D.托盘
