把以下句子变为一般疑问句和反问句：Trees help us in many ways.Trees keep the air cool and clean.

把以下句子变为一般疑问句和反问句：Trees help us in many ways.Trees keep the air cool and clean.
They take in harmful gasses from they air.
They are major fighters against air pollution.
I know trees make our lives more convenient.
Many of the things in our daily lives come from trees.
Tea comes from the leaves of trees.
A lot of furniture is made of wood.
I can imagine a world without trees.
We should stop doing this.