_____ be late again. [ ]
A. Try not to
B. Don’t try to
C. Try don’t to
D. Try not to
答案:A
下列各组物质不能用水来鉴别的是( )
A.CaCO3和 Na2CO3
B.K2SO4KNO3
C.生石灰和熟石灰
D.CuSO4和Fe2(SO4)3
通草纵剖面呈海绵状,对光照射可见亮银星。()