Did you often talk with your friends in English?
Old bottles or newspapers are also useful, so don't ___________.
学习地球运动时,老师在暗室里用电灯泡代表太阳,在电灯旁放置一个地球仪代表地球,模拟演示地球运动。读“地球运动演示图”,回答下列问题。