(A): Meso tartaric acid is optically inactive.
(R): Meso tartaric acid has no asymmetric carbon.

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(A) is false but (R) is true

Both (A) and (R) are true and (R) is the correct explanation of (A)

Both (A) and (R) are true and (R) is not the correct explanation of (A)

(A) is true but (R) is false

answer is C.

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Detailed Solution

Meso tartaric acid is optically inactive because it has a plane of symmetry that causes internal compensation of optical activity from its two chiral centers (asymmetric carbons). It does contain asymmetric carbons, but the molecule overall is achiral due to this symmetry, so it does not rotate plane-polarized light. This phenomenon is known as internal compensation.

Hence:

The reason for optical inactivity is internal compensation due to molecular symmetry, not lack of asymmetric carbons.
Meso tartaric acid has asymmetric carbons but is not optically active because of the internal mirror plane making the molecule superimposable on its mirror image.

This explains why statement (A) is correct and statement (R) is incorrect.

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