Self-study
Support Having an efficient, attractive subway system makes good economic sense. ███ ███ ████ █████ ██ ████████ ███ ██████ █████ █████ ███ ████ ██████ ██████ ██ ████ █████ ████ ████████ ██████
Summary
The city should purchase new subway cars. This is because having an efficient subway system makes economic sense. And the city should always do what makes economic sense.
Missing Connection
How do we know that new subway cars are necessary for an efficient subway system? Maybe an efficient system can be created with the existing set of cars. Consequently, to guarantee his conclusion, the author must assume that, if an efficient system is adopted, it will require new cars.
2.
The conclusion drawn above follows █████████ ██ █████ ███ ██ ███ █████████ ██ ████████
a
The city should ██████ ██ ██ ██████████ ██████████ ██████ ███████
This leaves open the possibility that the city could invest in a new system without investing in new subway cars. So (A) doesn’t guarantee the author’s conclusion.
b
Cost-effective subway cars ███ ██ ████████ ████ ██ ██ █████████ ██████ ███████
We don’t know if the new cars would be cost-effective, and we don’t know if the existing cars aren’t cost-effective. So this doesn’t guarantee the author’s conclusion.
c
Investment in new ██████ ████ █████ ██████ ████████ █████ ████ ████ ██ ███ █████ ██████████ ███████ ████ ██ ███ █████
We don’t know if this means investing in new cars makes economic sense. (C) leaves open the possibility that investing in new cars is a bad idea, but other options are even worse ideas.
d
New subway cars ███ ███████████ ███████████
Buying things that are affordable doesn’t always make economic sense. If an efficient subway system could be created while using the old cars, it wouldn’t be worthwhile to purchase new cars, even if they’re affordable.
e
New subway cars ███ ████████ ██ █████ ███ ███ ████ ██ ████ █ ██████ ██████ ████ ██ █████████ ███ ███████████
It would make economic sense to have an efficient subway system. The city should do whatever makes economic sense. So, if new subway cars are required for an efficient system, the city should get new cars. (E) guarantees the author’s conclusion.