Once from space the Great Wall is till great in sight.A. seeingB. to seeC. seenD. saw

问题补充：

Once from space, the Great Wall is till great in sight.

A. seeing

B. to see

C. seen

D. saw

答案：

A. seeing

B. to see

(答案→)C. seen

D. saw

解析：考查从句的省略式，主从句的主语一致时，可以省略从句的主语和be动词，once seen=once the Great Wall is seen，句意是：一旦从太空看，长城看起来还是很伟大。选C。