. The majority of the damage ______ easy to repair.
A.is
B.are
C.were
D.Be
答案:A
飞机上使用的交流电是().
A.220V50Hz
B.110V60Hz
C.115V400Hz
D.110V400Hz
在H2SO4和Al2(SO4)3的混合溶液中,铝离子浓度是0.4 mol/L,硫酸根离子浓度是0.7 mol/L,则氢离子浓度约是 [ ]
A.0.1 mol/L
B.0.2 mol/L
C.0.3 mol/L
D.0.4 mol/L