Which of the following expression represent the simplified form of Colebrook equation use to calculate the friction factor, if variable have their standard meanings?

A

$$ \frac{1}{\sqrt{f}} = 1.14 + 2 \log \left( \frac{K_s}{D} + \frac {9.35}{Re\sqrt{f}} \right) $$ 

B

$$ \frac{1}{\sqrt{f}} = 1.14 - 2 \log \left( \frac{K_s}{D} + \frac {9.35}{Re\sqrt{f}} \right) $$

C

$$ \frac{1}{\sqrt{f}} = 1.14 - 2 \log \left( \frac{K_s}{Re} + \frac {9.35}{D\sqrt{f}} \right) $$

D

$$ \frac{1}{\sqrt{f}} = 1.14 - 2 \log \left( \frac{K_s}{Re} + \frac {18.7}{D\sqrt{f}} \right) $$