Concept:Ozone is a different form of the element oxygen, known as an allotrope.
Explanation:Ozone has the chemical formula
O3​, unlike the common oxygen gas
O2​.
It exists as a pale blue gas with a pungent smell.
Ozone is made entirely of oxygen atoms, so it is not a compound or an isomer.
It is less stable than
O2​ and breaks down easily.
In the stratosphere, ozone forms a layer that protects Earth from UV rays.
Answer:A. an allotrope of oxygen