计算:x2•x3=______;2xy(x-y)=______.
x2•x3=x5;2xy(x-y)=2x2y-2xy2.
故答案为:x5,2x2y-2xy2;
下面哪种细菌一般不入血()
A.志贺菌
B.伤寒沙门菌
C.鼠疫耶尔森菌
D.布鲁杆菌
E.产单核李斯特菌
Nowadays people usually get ______ information from TV, newspaper and the Internet.[ ]
A. quite a few
B. a number of
C. a lot of
D. a pair of