The value of $$\frac{p^{2} - (q - r)^{2}}{(p + r)^{2} - q^{2}} + \frac{q^{2} - (p - r)^{2}}{(p + q)^{2} - r^{2}} + \frac{r^{2} - (p - q)^{2}}{(q + r)^{2} - p^{2}} is$$ is:

A

1

B

2

C

0

D

3