- Price of oil falls by half
→
Purchase price for gasoline made from oil will fall by half
There are a slew of assumptions being made here: (1) what if the companies want to simply make more money so they keep the prices the same? (2) what if there are other things that go into the price of oil that are unaccounted for? (3) Though a less likely outcome, what if the purchase price is determined by some other factor such as the consumer's willingness to pay and their willingness to pay is very consistent?
- (A) But using less gasoline has nothing to do with the purchase price. Do they pay less for that gasoline? Why not?!
(B) This one looked so tempting! However, it is actually more like the opposite of what we want. I gave this one a hard look until I understood that the answer choice was saying that the manufactures will NOT expand profit margins. In other words, if profit margins are NOT to be expanded, we could expect that the price of oil is going to fall dramatically.
(C) If anything this strengthens the conclusion by showing that the gasoline companies want to get their prices down as low as possible. While it may not bring the purchase price to half, there may not be much reason to doubt that it could.
(D) With some tweaking, this could have been a great answer but we aren't concerned with how much gasoline people are buying. We are concerned about the price of gasoline. In addition, this is kind of already assuming the oil analysis's conclusion as a premise. It is saying (purchase price fallen → more gasoline bought). Instead, we want something more with the structure of (__________ → purchase price not fallen)
(E) This definitely weakens the conclusion! It shows that there is MORE to gasoline prices than simply the oil. There are all these costs associated and - even more importantly - these costs DO NOT vary significantly AND "constitute a large portion of the price." If this is true, can we really say that if the price of oil falls by half then the price of gasoline will fall by HALF, too? It would almost impossible to say that! We have to think about all those other costs that DO NOT vary much!