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

Kids talk frequently about what they can do, __________ many adults do the opposite, tending to talk about what they can’t and why.

The members of the board are discussing the problem right now; it will _____ have been solved by the end of next week．

“Perhaps we need to send for Dr. Smith to see what we can do about it,” Father suggested ________ to his neighbor who had come to discuss the problem.

.--- Robert, you didn’t travel by train?--- I was going to, but then I decided to go by car______.