The correct option is option 1 - Allotropes.

Allotropes are different forms of an element that have the same chemical composition but different physical properties. Oxygen and ozone are both forms of elemental oxygen, but they have different molecular structures and properties.

Oxygen (O2) is a diatomic molecule, meaning it consists of two oxygen atoms bonded together. It is a colorless and odorless gas at room temperature and is essential for supporting life.

Ozone (O3), on the other hand, is a triatomic molecule consisting of three oxygen atoms bonded together. It is a gas with a pungent odor and a bluish color. Ozone is commonly found in the Earth`s upper atmosphere, where it plays a vital role in protecting us from harmful ultraviolet radiation.

Therefore, oxygen and ozone are considered allotropes of each other because they are different forms of the same element, oxygen, with distinct physical properties.