已知集合A={0,1},B={z|z=x+y,x∈A,y∈A},则B的子集个数为( )
下列关于激素特点的叙述中,正确的是( )
________I admit the boy has a gift for music,I don't think he will make a good singer.
有关青藏地区的叙述,正确的是( )