Answer:
What has four wheels and flies?
I am milky white and scares people.
I have a mouth on my head and eat everything.
What comes once in a year twice in a week but never in a day?
You can see it everyday, but cannot touch it at will. What is it?
Who makes it, has no need of it. Who buys it, has no use for it. Who uses it, can't see it. What is it?