In the binomial expansion of $$(a - b)^n, n \ge 5$$, the sum of $$5^{th}$$ and $$6^{th}$$ terms is zero, then $$\frac{a}{b}$$ equals

A

$$\frac{5}{n - 4}$$

B

$$\frac{6}{n - 5}$$

C

$$\frac{n - 5}{6}$$

D

$$\frac{n - 4}{5}$$