How is blood flow related to lung function during exercise?
blood vessels are dilated to increase the amount of oxygen carried in the blood, and the lungs work harder to meet the body's oxygen demands.
blood volume increases during exercise, making the body more efficient, so it is not necessary for the lungs to work as hard.
the lungs determine the speed at which the heart pumps, so blood flows at a level that accommodates oxygen absorption in the muscles.
the lungs expand and contract, which increases the rate of blood flow so the muscles can convert stored energy to energy for muscle movement.

Answer;

Blood vessels are dilated to increase the amount of oxygen carried in the blood, and the lungs work harder to meet the body's oxygen demands.

Explanation;Blood flow is greater during exercise because the blood vessels in the muscles dilate.During the exercise the body needs large amounts of oxygen, glucose, amino acids, and a molecule called ATP to allow the muscles to contract and do work. As the muscles consume nutrients and perform work waste materials like lactic acid are produced and need to be carried away from the muscles, so they can be metabolized by the liver and eliminated or recycled.  It is because of this need to bring in large amounts of materials and remove waste products that blood flow increases dramatically during exercise.