Let \(g(x)=\int_{x}^{2 x} \frac{f(t)}{t} d t\) where \(x>0\) and \(f\) be continuous function and \(f(2 x)=f(x)\), then
(A) \(g(x)\) is strictly increasing function
(B) \(g(x)\) is strictly decreasing function
(C) \(g(x)\) is constant function
(D) \(g(x)\) is not derivable function