现代照相机的前身是什么?
参考答案：
用针孔成像的原理制成的针孔成像箱，将暗箱后端的白纸光屏换成底片。
用括号里的词的适当形式填空。
1.I’d like ______ (organize) a party.
2.She _______ (play) the piano for 2 hours.
3.When I was twelve,I _______ (start) to play tennis.
4.My brother has been swimming since he _______ (be) 7 years old .
5.Their apartment is on the _______ (nine) floor of the building .
6._______ (luck)，Fred was not hurt in the car accident .
恢复定线工作的主要内容是什么？
