Which of the following organisms do not have bones and moves with the help of contraction and expansion?

Correct option is A

The correct answer is Earthworms.
Movement in earthworm
• The body of earthworm is made up of many rings joined end to end.
• It has muscles which help to extend and shorten the body.
• Under its body it has large number of bristles called setae which are connected with muscles.
• These bristles help to get grip on the ground.
• During movement, the earthworm first extends the front part of the body, keeping the rear portion fixed to the ground.
• Then it fixes the front end and releases the rear end.
• It then shortens the body and pulls the rear end forward.
• This makes it move forward by small distances.
• Repeating such muscle contraction and relaxation the earthworm can move through soil.
• A slimy substance secreted by its body helps this movement.