I don’t know if you noticed their absence or not, but we ________.

____ I admire David as a poet, I do not like him as a man.

Only after he had spent several nights working on the math problem _______ to wonder whether the problem was wrongly set.

I know the boy very well. I have seen him＿＿＿＿up from childhood. 

Not until all the fish died in the river ______ how serious the pollution was.