A particle moves according to the law $$x = at$$, $$y = at(1 - \alpha t)$$ where a and $$\beta$$ are positive constants and t is time. The time instant at which velocity makes an angle $$\frac{\pi}{4}$$ with acceleration is

A

$$\frac{4}{\alpha}$$

B

$$\frac{3}{\alpha}$$

C

$$\frac{2}{\alpha}$$

D

$$\frac{1}{\alpha}$$