A:牛耕
B:蒸汽机
C:内燃机
D:互联网
m=a+a+5,n=a+2+a+3a>0,则有( )
肾脏的结构和功能单位叫做肾单位,每个肾单位由____、____和____等部分组成.
The students ____ ____ ____ Chinese in their classroom now.