治理雾霾，人人有责。如果每个人少开一天车，多植一棵树，少放一挂鞭，多省一度电…… 个人之力虽微，但一点一滴汇聚起来，就是强大合力。因此
某同学准备用反证法证明如下一个问题：函数在上有意义,且,如果对于不同的,都有，求证：。那么他的反设应该是___________．
（06年安徽卷文）“”是“的（）A．必要不充分条件 B．充分不必要条件C．充分必要条件 D．既不充分也不必要条件
Two-year-old Christopher Merrett has such severe food allergies that even the smell can send him into potentially deadly shock． Mrs．Merrett said she first _________ something was wrong with he
单斜硫和正交硫是硫的两种同素异形体。 已知：①S(s，单斜) + O2(g) = SO2 (g) △H1= -297.16kJ·mol-1 ②S(s，正交) + O2(g) = SO2 (g) △H2= -296.83kJ·mol -1 下列说
胡主席指出，中央政府对香港、澳门采取的任何方针政策措施，都会始终坚持有利于保持香港、澳门长期繁荣稳定，有利于增进香港、澳门全体市民福
There was one thought that air pollution affected only the area immediately around large cities with factories and heavy automobile traffic. At present, we realize that although these are the areas
在下列实例中，分别属于相对性状和性状分离的是（ ） ①狗的长毛与卷毛 ②兔的长毛和猴的短毛 ③人的单眼皮和双眼皮 ④高茎
