28. The principal reason for turbocharging is to increase the power output of an engine ofgiven size and speed, by enabling the cylinders to be charged with air at an elevated pressureand, therefore, at a higher density than air at atmospheric pressure. What is the main purpose touse a turbocharger？
(A) To elevate the density of air in order to decrease the pressure in cylinder.
(B) To elevate the pressure of air in order to decrease the density in cylinder.
(C) To improve the power output of an engine of given size and speed by increasing thecompressed air intake temperature.
(D) To improve the power output of an engine of given size and speed by increasing the density ofcharged air.