A particle moving along a straight line has a velocity vms^-1, when it has cleared a distance y meter. These two are connected by the relation $\mathrm{v}=\sqrt{49+\mathrm{y}}$. When its velocity is 1ms^-1, its acceleration(in ms^-2) is

• A

  1

• B

  2

• C

  7

• D

  1/2