When his mother came in, the boy pretended ____.
If he takes on this work, he will have no choice but _____ an even greater challenge .
A lot of exercise outdoors could _____ positive energy which helps you to reduce stress.
If anyone knows of recent research about this topic, I would greatly appreciate_____.
I don’t think he is the right person to do that job, _____?
--- How did he lose much weight?--- _____ eating less, he walked ten miles every day.