A wire of length L and radius a rigidly fixed at one end. On stretching the other end of the wire with a force F, the increase in its length.is /. If another wire of same material but of length 2L and radius 2a is stretched with a force 2F, the increase in its length will be:

• A

  l/4

• B

  l

• C

  l/2

• D

  2l