A:My sister is very old.
B:My brother is very young.
C:My sister is very young.
下列关于O2的说法中,正确的是( )
若单项式13xn+1y与单项式3xyz乘积的结果是一个六次单项式,求n的值.
Some experts believed, and _______ did we, kids who reach adolescence still need at least nine hours' sleeping.
伊拉克与伊朗的战争原因主要是( )