If the point $$\left(\alpha, \frac{7\sqrt{3}}{3}\right)$$ lies on the curve traced by the mid-points of the line segments of the lines $$x \cos\theta + y \sin\theta = 7$$, $$\theta \in \left(0, \frac{\pi}{2}\right)$$ between the co-ordinates axes, then $$\alpha$$ is equal to

A

$$-7$$

B

$$-7\sqrt{3}$$

C

$$7\sqrt{3}$$

D

$$7$$