I believe the passage doesn’t state that half of all automobiles on the road were produced by Deluxe. The passage states that “over half of all automobiles BUILT BY THE COMPANY since 1970 are still on the road today.” Therefore, I believe it is irrelevant how many cars were produced by Deluxe. I went with D only because it sounds better than B.
This one is definitely B, although D can be quite tempting. Here is a little trick to show clearly that the answer is D.
The question asks which answer choice strengthens the argument that Deluxe automobiles are more reliable than other cars, due to the fact that a higher percentage of Deluxe cars are still on the road.
The correct answer will make the conclusion MORE believable. Using a trick to properly identify assumptions, let's negate the answer choice (make the statement the opposite) to see if the conclusion becomes LESS believable.
B - The number of automobiles built by deluxe each year HAS
increased sharply since 1970.
If the number of autos has increased sharply in recent years it would be very easy for a higher percentage to still be on the road so the conclusion that Deluxe autos are more reliable is much, much LESS believable. B is the correct answer. [also see good explanation from ConnectTheDots above]
D - Since 1970, Deluxe has made
MORE changes in the automobiles it manufactures than other car companies have made in their automobiles.
This is interesting information, but it doesn't make the conclusion less believable. Cars were chunks of iron with wheels in the 70's and have experienced massive amounts of change over the years. In fact, we might expect more change from reliable car manufacturers. The amount of change does not cast doubt on reliability so D is not the correct answer.
Additionally, watch out for time when CR questions discuss both percentages and raw numbers. The GMAT loves to trap people in the shift between percentages and numbers.
Kyle Widdison | Manhattan GMAT Instructor | Utah
Manhattan GMAT Discount | Manhattan GMAT Course Reviews | View Instructor Profile