________Tom________ Mary speaks good Chinese, so they can talk with these Chinese students very well.
A:Not; but
B:Not only; but also
C:Both; and
D:Either; or
世界各大洲中,人口自然增长率最高的是
细菌与动植物细胞的结构相比,最主要的区别是( )
当二次函数y=x2+4x+9取最小值时,的值为( )