The old man was very happy__his wife in the hospital.(see)为什么?为什么不用to saw?

The old man was very happy__his wife in the hospital.(see)为什么?为什么不用to saw?
The old man was very happy__his wife in the hospital.(see)
为什么?
为什么不用to saw?

The old man was very happy__his wife in the hospital.(see)为什么?为什么不用to saw?
to see
动词不定式是 to+do(动词原形)的形式
saw是过去式,不能出现在不定式中

to see 不定式作原因状语
i am glad to see you一样的句式

to see

表示看到某事的反映， BE + adj（glad, pleased, happy, sad, shocked,surprised 等）+at +sth 或者 + to +V