Assertion: Locomotion in Hydra is carried out by two types of contractile cells.
Reason: Muscle fibres are lacking in Hydra.

Options

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

Answer

A

Explanation

As muscle fibres are lacking in Hydra, the animal uses two types of contractile cells for this purpose. Processes of these cells run in the body wall both along the long axis of the body and arround the central body cavity. Contraction and releaxation of these cells respectively. shorten and elongate these processes. They consequently cause all types of movement of Hydra including shortening, elongation and also bending of body and tentacular movement Locomotion is carried out by somersaults looping.