根据句意及汉语提示填空.
_________ __________the answer can help you understand the passage.( 找出)
The car slowed down in time and _________ _________ into the wall. (避免撞击)
He _________ _________his son once a week.(收到……来信)
They _________ _________those problems by themselves at last. (处理)
It's _______ ________to clean the classroom.(轮到我们)
