A particle moves in the XY-plane according to the law $x=kt,y=kt(1-\alpha t)$, where k and $\alpha$ are positive constants and t is time. The trajectory of the particle is

• A

  y = kx

• B

  y = x $- \frac{\alpha x^2}{k}$

• C

  y =  $- \frac{a{x}^2}{k}$

• D

  y = $\alpha$x