— .Look at the sign. It says "No Smoking".
A:Of course not
B:Never mind
C:No, I don't
D:You'd better not
下列各式中,代数式的个数为( )
①b;②13;③x>5;④1x+2.
如图中,几何体的截面形状是( )
商品谷物农业和大牧场放牧业的共同优势及特点是( )