Assertion: Lactic acid is optically active

Reason: A symmetry in the inner structure of organic compounds causes optical activity.

• A. Both assertion and reason are correct and the reason is the correct explanation of the assertion.
• B. Both assertion and reason are correct but reason is not the correct explanation of the assertion.
• C. Assertion is correct but reason is incorrect.
• D. Both reason and assertion is incorrect.

Lactic acid is indeed optically active due to its chiral structure, which means it has a non-superimposable mirror image. This chirality allows it to rotate plane-polarized light. However, the reason provided about symmetry in the inner structure of organic compounds causing optical activity is not accurate, as optical activity arises specifically from chirality, not symmetry.

Answer Analysis

• Assertion: Lactic acid is optically active. (Correct)
• Reason: A symmetry in the inner structure of organic compounds causes optical activity. (Incorrect)

Final Choice

The correct answer is C: Assertion is correct but reason is incorrect.