Which gas do humans exhale when they breathe out?

What is the main source of Vitamin D for humans?

What do we use to clean wounds to kill germs?

Which gas is used in cooking gas (LPG)?

Which gas is necessary for burning?

What type of energy is used in electric bulbs?

Which gas is filled in balloons to make them float?

Which disease is caused by mosquito bites?

Which disease is prevented by drinking boiled water?

Which type of mirror is used in vehicles to see traffic behind?