Assertion: molluscs have ctenidium.
Reason: Ctenidium acts as the respiratory organ.

Options

A. If both assertion and reason are true reason is the correct explanation of assertion
B. If both assertion and reason are true but reason is not the correct explanation of assertion
C. If assertion is true but reason is false
D. If both assertion and reason are false.

Answer

B

Explanation

Both assertion and reason are true but reason is not the correct explanation of assertion
Clenidium is a monopectinate gill situated on the right side of the branchial chamber. Ctenidium helps in respiration by heating of cilia, thus creating water current. Ctenidium is innervated by nerves from the left supply indicates that it is actually an organ of the left side but has shifted to the right side during development (torsion). Torsion or twisting is a development of gastropods, which rotates the visceropallium anticlockwise through out `180^(@)` from its initial position , so that mantle cavity with its pallial complex, is brought in front of the body in adult.