the sun rising slowly in the east, the scene is a perfect dream.
A. Seeing
B. To be seeing
C. When you see
D. Having seen
网友回答
A. Seeing
B. To be seeing
(答案→)C. When you see
D. Having seen
解析：从句主语为the scene ，主句为you ，只能写成主从句。其他选项不合适
“当你看到太阳从东方慢慢升起时，这种景色确实太美了 ”