This problem is full of conditional logic. Let’s take a closer look at answer choice C, and the logic given in our stimulus. We get answer choice C from the second sentence of the stimulus, where it tells us what is sufficient for a tax to be considered ineffective.
Stimulus: (Second sentence of the stimulus) If a tax does not raise revenue AND if a tax costs a significant amount of money to enforce —> a tax is ineffective
Answer choice C: The tax on gasoline costs a significant amount of money to enforce. (The second part of the sufficient conditions is met.)
Thus, if it does not raise revenue (the first part of the sufficient condition)... —> then you get the necessary, that the tax is ineffective.
We are first told the second part of the sufficient condition to an ineffective tax is met. If the first part is also met, then our sufficient condition is met entirely, which guarantees the necessary, which in this case is an ineffective tax.
Hope this helps! Feel free to follow up if you have anymore questions.
