生命在生物圈中的延续和发展,最基本的环节是( )
A:生殖
B:遗传
C:生殖和发育
D:发育
Their mothers often them.
下图中人物的主要贡献是( )
A .How old are you?
B .I'm ten,too.
C .I am ten.
D .My name's Mimi.
E .What's your name?