What you cannot hold but it is yours?

A seven-year-old kid challenged his classmates that he can make the number one disappear by adding something to it.

How can he do that?

John is the son of Jacob.
So,
Jacob is the_____of John's father?

What number divided by 4 is the same as that number minus 4?

Always in you, Sometimes on you;

If I surround you, I can kill you.

What am I?

I cannot talk, but I always reply when spoken to. What am I?

Count the number of balls in picture below:

The barber of Town shaves all men living in the town. No man living in the town is allowed to shave himself. The barber lives in that town. Who then shaves the barber of the town?

Imagine you are in a room with no windows or doors. How will you get out?

What Adam and Eve do not have but the rest of the people have?