If x + a is the highest common factor of $$x^2 + bx + c$$ and $$x^2 + dx + e$$, then the value of a is

A

$$\frac{c - e}{b - d}$$

B

$$\frac{b - d}{c - e}$$

C

$$\frac{c + e}{b + d}$$

D

$$\frac{b + d}{c + e}$$