Assertion (A): Ozone (O₃) found at higher levels of the atmosphere is beneficial, while at ground level it is…

Question

Assertion (A): Ozone (O₃) found at higher levels of the atmosphere is beneficial, while at ground level it is a poison.
Reason (R): At higher altitudes, ozone shields living organisms from harmful UV radiation; at ground level it is toxic to aerobic life.

Options:
(A) Both A and R are true and R is the correct explanation of A.
(B) Both A and R are true but R is not the correct explanation of A.
(C) A is true but R is false.
(D) A is false but R is true.

Accepted Answer

## Model Answer **(A) Both A and R are true and R is the correct explanation of A.** Ozone is a deadly poison at ground level but shields Earth from harmful UV radiation at higher altitudes, so R correctly explains A. ## Explanation The textbook explicitly states that ozone "is a deadly poison" but at higher atmospheric levels "shields the surface of the earth from ultraviolet (UV) radiation." The Reason directly explains *why* the Assertion is true — making option (A) the correct choice. Examiners expect students to verify both the truth of A and R, and whether R logically explains A.

Science (086) — AI-generated practice question