早期发育
参考答案：指噬菌体侵染中在DNA复制起始前的一段时期。
选词填空。
1. Danny is _______ basketball now.
2. The baby is ________ fun.
3. She's _______ the newspaper.
4. He isn't _______ now.
在画车间平面图时，其比例通常为( )。
A．1:1
B．1:50
C．1:100
D．1:200
