商店有l50千克香蕉,上午卖出50千克,下午卖出70千克,现有香蕉多少千克?( )
150-(50+70),
=150-120,
=30(千克);
答:现有香蕉30千克.
I have to eat _____ food than before, or I'll get fatter and fatter. [ ]
A. a few
B. fewer
C. less
D. little
区分盐酸吗啡与磷酸可待因的反应选用()
A.Marquis反应
B.Frohde反应
C.与稀铁氰化钾试液氧化还原呈色反应
D.与香草醛的呈色官能团反应
E.与发烟硝酸共热的硝基取代呈色反应