Don laugh ______ your classmate. You shoud help him.A.atB.inC.on

Don’t get your schedule _________

The purpose of teaching your classmates is to______.A．show you have mastered the knowledge

Mary looks unhappy because she has ______ by her classmates.A、laughedB、laughed atC、been

________（47）A.Don’t eat food in your car.B.Don’t

________（48）A.Don’t eat food in your car.B.Don’t

________（49）A.Don’t eat food in your car.B.Don’t