Knowledge is to one’s mind ______ food is to one’s body.
The fact that many college graduates get lower pay than some workers has ______ a heated discussion.
I have no idea ______ it is that makes him puzzled.
He sat at the desk, __________ a novel.
______ tourism developing, more and more people prefer to go travelling for a holiday.
.--- I was lucky the win a gold medal in the800-metre race.--- You ____ through hard training.