What is the indefinite integral of (1)/(sqrt(1+49x²))?

A) ∫ (1)/(sqrt(1+49x²)) dx
B) ∫ (1)/(7sqrt(1+7x²)) dx
C) ∫ (1)/(sqrt(1+7x²)) dx
D) ∫ (1)/(7sqrt(1+49x²)) dx