Professor Lee failed many times but he ________found a good way to solve the problem.

Ben has not the least_______ of giving up his research.

Though some foreign scientists had a ______ opinion of his new invention, his fellow workers never thought ____ of it.

It seems that living green is               easy and affordable. A small step makes a big difference.

 When we got there, he was about to leave, so he only had time to explain _____ to us what he thought of our plan.