She saw it go down a hole.

这句话的意思是我看到它滚落到了一个坑里.
你要是用从句的话,意思就是我看出.
see sth do 是看到某人（东西）做某事
see +that 就是看出的意思.I see that you have just cried.我看出你刚刚哭过.I see him crying.我看到他哭了.
所以你要用 She saw it went down a hole.就成了我看出它掉坑里了.