Which of the following statements is correct?

A- The major rivers of the country generally retain better water quality in densely populated stretches of plains.

B- In plains, river water is used intensively for irrigation, drinking, domestic and industrial purposes.

Only statement b is correct.

Available water resources are degrading rapidly. The major rivers of the country generally retain better water quality in less densely populated upper stretches in hilly areas. In plains, river water is used intensively for irrigation, drinking, domestic and industrial purposes. The drains carrying agricultural (fertilizers and insecticides), domestic (solid and liquid wastes), and industrial effluents join the rivers.