Let $$f(x) = \int_0^x g(t) \, dt$$, where $$g$$ is a non-zero even function. If $$f(x + 5) = g(x)$$, then $$\int_0^x f(t) \, dt$$ equals:

A

$$\int_5^{x+5} g(t) \, dt$$

B

$$\int_{x+5}^5 g(t) \, dt$$

C

$$5\int_{x+5}^{5} g(t) \, dt$$

D

$$2\int_5^{x+5} g(t) \, dt$$