Which structure in the heart prevents the backward flow of blood between chambers?

Which simple machine is used in a pair of scissors?

Which everyday phenomenon explains why a wet cloth dries faster on a windy day compared to a calm day?

Which gas commonly used in refrigerators and air conditioners was historically linked to ozone layer depletion?

Which type of teeth are primarily used for tearing food in humans?

Which everyday chemical process explains why sliced apples turn brown after being exposed to air?