The correct answer is A) Increasing the volume of the exhaust gases. The divergent area of the exhaust duct is designed to expand the cross-sectional area of the exhaust gases as they exit the engine. This expansion causes the velocity of the gases to decrease while the volume increases, in accordance with the principle of conservation of mass. Increasing the volume of the exhaust gases aids in the overall efficiency of the engine by reducing backpressure and improving the flow of gases out of the engine. The other options are incorrect because: B) Increasing the pressure would be the opposite effect of what the divergent duct is designed for; C) Decreasing the volume would go against the intended purpose; and D) Increasing the velocity would also be the opposite of the divergent duct's function.