To permit a large water flow , the pipe must have, a. enough strength, b.a large cross sectional area, c. enough length to conduct the flow or ,d. a sufficient drop

B. A large cross sectional area,

Explanation:

To permit a large flow of water in a pipe, the cross sectional area of the pipe must be significantly large. According to the flow rate equation:

                    V =

Where:

           Q is the Volume flow rate and it is the volume of fluid that flows              through the pipe

            V is the velocity of the fluid in the pipe

            A is the cross sectional area of the pipe.

From the equation, we see that for a larger amount of water to flow in a pipe, the cross-sectional area must be very large. In short, Q varies directly as A.