In this task, you are given a multiple-choice question and you have to pick the correct option. Answer with option indexes (i.e., "A", "B", "C", and "D").
Q: Laser anemometers help manufacturers of cars, airplanes and spacecraft to produce efficient vehicle designs that (A) increase the gas mileage of the vehicles (B) increase the drag from air moving past them (C) decrease exhaust fumes from the vehicles (D) reduce resistance from air moving past them
A:
D