The cause he had devoted himself to __________a perfect success

Mr. Lee ____ to a student when I entered theclassroom this morning.– He is very patient ____he is young.

What would have happened＿＿＿＿, as far as the river bank?

Would you care for a drink— No, thanks. I ___________.

I think it’s impossible for us to work out the plan in just two days. It’s too difficult.—You’re right. We can’t be _______ careful while working on it.