我国秦岭——淮河一线以北的地区( )
A:冬季河流多要结冰
B:为亚热带
C:属于我国非季风区
D:为湿润区
It wasn't easy having my friends talk about their freshman years____ I wasn't a part of.
下列式子中:2,2a,3x﹣1,3s+9t,s=12ab,x+y>4,m2,代数式有( )