New Critical Reasoning question bank by carcass

hii carcass i have doubt in the following question
A bullet train travels in excess of 150 miles per hour. Therefore, if a train travels slower than 150 miles per hour, it is not a bullet train.
Which of the following most closely parallels the reasoning used in the argument above?
A) An orange ripens only on the vine. If it ripens on the vine, then it is not an orange.
B) Newspapers are often read by more than one person. Therefore, magazines are also likely to be read by more than one person.
C) An earthquake of 5.0 or above on the Richter scale causes massive damage. If there is not massive damage, then the earthquake did not attain a 5.0 or above.
D) A supersonic plane travels at speeds in excess of Mach 1. If it is not supersonic, then it will travel at speeds below Mach 1.
E) Fluoride generally prevents cavities. If there are no cavities, then there was no fluoride used.

its explaination is as follows:
C
To answer this parallel-the-reasoning question, you have to break down the original argument, and then find an answer choice that mimics it exactly. In this case, the argument says a bullet train travels in excess of 150 miles per hour (if A, then B). Therefore, if a train travels less than 150 miles per hour, then it is not a bullet train (if not B, then not A). Now all you have to do is find an answer choice that mimics that reasoning exactly. Choice A, broken down, reads, “if A, then B … so if B, then not A.” This isn’t it. Eliminate it. Choice B breaks down to “if A, then B … therefore C will also cause B.” That’s not it either. Choice C breaks down to “if A, then B … therefore if not B, then not A.” This is the best answer. Choice D might seem tempting because it also has to do with a fast means of transportation, but what counts here is the reasoning: if A, then B … if not A, then not B. This is close, but no cigar. Choice E is also appealing; you may even think it mimics the argument exactly. But there’s a trick. The first half of the sentence reads, “Fluoride generally prevents cavities” (if A then B). Note that the B part is about the prevention—not the presence—of cavities. So the second half, “If there are no cavities, there was no fluoride,” actually breaks down to “if B, then not A.”


doubt- i think in e also if a(flouride) then b(cavities) and if not b(not cavities) then not a(not flouride) is valid...so it is creating confusion in my mind..please help me