The joke is funny.
A:makes you jump
B:makes you laugh
C:makes you feel comfortable
已知集合A={0,1,a},B={2,a2},若A∪B=0,1,2,3,9,则a的值为( )
下列化学仪器需垫加石棉网才能用酒精灯加热的是 ____ ,能直接加热的是 ____ (填序号).
A.试管 B.烧杯 C.燃烧匙 D.蒸发皿 E.锥形瓶 F.圆底烧瓶.
读我国南、北方地区水资源和耕地资源比例示意图,完成以下小题.