人类的性别由性染色体决定。男性体细胞中的性染色体为 ,能产生 种精子。女性体细胞中的性染色体为 ,能产生 种卵细胞。
When we go abroad, we can see many things (make) in China.
China Daily is worth (read), we can learn a lot from it.
Did you hear anything (usual) in the next door?
No, I was chatting online with friends.
I want to invite some of my friends to my (twenty) birthday party.
My bike is broken. I want to get it (repair).