We can eat in the dining hall. But we _______ eat in the classroom.
I’d like to travel by air _________ it usually costs a lot of money.
For the safety, everyone _________ obey the traffic rules when he is driving or walking.
This summer vocation I am going to do a lot of _________ to prepare for the senior high school.
--Did you see Mary and her sister this morning? -- Yes, I saw _________ girls playing in the playground.
Although advertisements enable _________ to make decisions quickly, they sometimes cause lots of trouble.