Replace the question mark with the correct number.

What have one eye but still cannot see?

What's a single-digit number with no value?

My friends called me Iron59 because my parents are a chemist and a mathematician. What is my real name?

John’s parents have three sons: Snap, Crackle, and what’s the name of the third son?

You have a three-gallon and a five-gallon measuring device. You wish to measure out four gallons.

A man was driving a black truck. His lights were not on. The moon was not out. A lady was crossing the street. How did the man see her?

It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

Five lovely ladies(Sophia, Isabella, Madison, Emma and Olivia) planned a picnic.

They each buy one thing each for the picnic.

Sophia, Emma and Olivia got a drink : orange-Juice, apple-juice, and mango-juice.
Olivia got the drink with the same letter as the one in her first name.
Emma loves mango-juice.
The other two bring some food : chocolates and pizza.
Also Madison is allergic to cheese.

So which ladies bought what ?

If Bihan is 10, Anirudha is 20, and Kim and Seal are both 5, but Rikold is 10, how much is Kenniger by the same trend?