The correct answer should be <span>a) Drive more than 500 miles on one tank of gas.
This is because fuel efficiency is a focal point in this answer, while D. deals with fuel efficiency, but that is not the main point of the advertisement. </span>
The answer is A: Drive more than 500 miles on one tank of gas.
The data of sentence A<em> </em><em>shows specifically how far a car can go with one</em><em>tank of gas</em>. In sentence D, it's just mentioned that people are tired of the 20 mile per gallon efficiency. In sentence B, <em>leg room</em> is the space for the legs in the car. In sentence C, the information that more than 30 engineers worked in a car <em>doesn't</em> prove increased fuel efficiency.