Thanks for the question! So we’re told here that having an efficient, attractive subway system makes good economic sense. So (this indicates what follows is a conclusion) the city has to purchase new subway cars, since it should always do what makes good economic sense.
Now we’re looking for something that, if assumed, will make the conclusion follow logically. In other words, this is a strengthen with sufficient premise question. Well, we know that the city should always do what makes good economic sense, and having an efficient, attractive subway system makes good economic sense. We want to conclude that the city needs to purchase new subway cars. And nothing currently in the argument connects to the idea of purchasing new subway cars, so the answer choice has to do that for us. Now take a look at (E), which tells us that new subway cars are needed for the city to have an efficient and attractive subway system. Well, if that’s true, then the city does need to get the new subway cars! And that’s what makes (E) correct.
Hope this helps! Feel free to ask any other questions that you might have.
