____from space,our earth,with water covering 70% of its surface,appears as a "blue plane".

问题描述:

____from space,our earth,with water covering 70% of its surface,appears as a "blue plane".
选项有 a.seeing b.to be seen c.seen d.have seeing
选什么,为什么啊

c.seen
这是过去分词做地点状语,相当于If it's seen...