Previously, most vehicle manufacturers ignored fuel efficiency in favor of speed and performance. Fuel efficiency was difficult to engineer and manufacturers paid little attention to excessive fuel consumption in developing their designs. This year the most sold vehicle in the United States has been the most fuel efficient one—a certain sign that manufacturers are becoming more concerned with limiting wasteful fuel usage than optimizing a vehicle’s speed.
Which of the following, if true, most seriously weakens the argument above?
【选项】
Recent improvements in the process of vehicle design and materials have made fuel efficient vehicles faster than less fuel efficient equivalents.
选项是否正确？