what season is the most dangerous ?why?

1.What season is the most dangerous one? --fall(if always fall in the fall,then i think the season is a nightmare. )
2.What is easy to get into but hard to get out of?---problem
3.What is smaller than an insect mouth?---the teeth in the insect's mouth Ha.../ hair
4.What is white when it is dirty?-----blackboard
5.Which four letters is the thief afraid of?---stop
6.Why is a river very rich?----Beats me.I've no idea
7.Two little brothers,one lives on one side,the other on the other side,they hear what you say,but they do not see each other.---ears

the sixth question, the answer is .... the river has two banks......

Fall
秋天，也是掉下来的意思，所以危险

fall,秋天

因为fall有跌倒的意思

最危险的季节是什么，为什么