If $$a + b - c = 0$$, then what is the value of $$\frac{(b - c)^2}{4bc}\frac{(c - a)^2}{4ca}\frac{(a + b)^2}{4ab}$$?

A

$$\frac{1}{2}$$

B

$$-\frac{3}{4}$$

C

$$-\frac{1}{2}$$

D

$$\frac{3}{4}$$