2-（-1）的结果是（ ）
A．-1
B．1
C．-3
D．3
2-（-1）=2+1=3．
故选D．
I _______ you for sixteen years and I still don't know what goes on in your mind. [ ]
A. have married
B. have got married to
C. have married with
D. have been married to
己知反应3A＋2B 2C+D，A、B两物质完全反应时的质量比为3：4，若生成C和D共140g，则该反应消耗B的质量为
A． 60g B．80g C．90g D． 120g
2C+D，A、B两物质完全反应时的质量比为3：4，若生成C和D共140g，则该反应消耗B的质量为