ANS:A -

Reynolds analogy is an empirical relationship that relates the Stanton number (St) to the friction factor (f) in turbulent flow. The general form of Reynolds analogy is: 2(1+)St=2f​(1+A) Where A is a constant that depends on the flow regime and geometry. For fully-developed turbulent flow in a pipe, A is often taken to be 0.5. So, the correct relationship is: 2(1+0.5)St=2f​(1+0.5) St=23​f Therefore, the correct statement is: St=23​f