The system with the transfer function $$\frac{Y(s)}{X(s)}=\frac{s}{s+p}$$ has an output $$y(t) = \cos \left(2t - \frac{\pi}{3}\right)$$ for the input signal $$x(t) = p \cos \left(2t - \frac{\pi}{2}\right)$$.Then the system parameter p is

A

$$\sqrt{3}$$

B

1

C

$$\frac{2}{\sqrt{3}}$$

D

$$\frac{\sqrt{3}}{2}$$