平行移动拍照法
参考答案:
与被拍物体呈现平行状态连续拍照。
We _______ on it for several hours but we have not yet reached any conclusion.
A.work
B.areworking
C.havebeenworking
D.havebeenworked
连接装置的作用是什么?对其有哪些要求?