按要求完成句子。
1.Smoke makes the air dirty.(对画线部分提问)
________ ________the air dirty?
2.They put rubbish in the bin.(改为否定句)
They________ ________rubbish in the bin.
3.We go to school on foot.(改为同义句)
We________ ________school.
4.Helen cleaned the classroom yesterday.(改为一般疑问句)
________Helen ________the classroom yesterday?
5.makes, black, from, air, factories, smoke, the, dirty(.)(连词成句)
______________________________________________