---Why don’t you use the knife? ---It needs ___________________.
He left home without saying a word, and _______ worries many people and is to be found out.
He came all the way to China for learning it better _______ for making money.
Evidence gained from observation and experiment is often used to _______ a scientific theory.
_______ be sent to work there?
—That must have been a long trip.—Yeah, it _____ us a whole week to get there.