Self-study
Support Maria won this year's local sailboat race by beating Sue, the winner in each of the four previous years. ██ ███ ████████ ████ ████ ████ █████ ███████ █████
Summary
Maria must have trained hard. This is because she beat a repeat previous champion, Sue, at the sailboat race.
Missing Connection
How do we know that training hard was the only way Maria could have won? Maybe she won because of better equipment, greater natural talent, or more willingness to cheat. Consequently, to guarantee his conclusion, the author must assume that hard training is necessary to beat a champion.
23.
The conclusion follows logically if █████ ███ ██ ███ █████████ ██ ████████
a
Sue did not █████ ██ ████ ██ █████ ████████
This tells us that Maria trained, and trained relatively harder than Sue. But it doesn’t tell us that Maria trained objectively hard—it’s possible that Sue didn’t do any training.
b
If Maria trained █████ ███ █████ ███ ███ ████████ █████
This lets us make an inference if we already know that Maria trained hard (sufficient condition); it doesn’t tell us anything if she won the sailboat race (necessary condition).
For example, if all Maria’s opponents were sick on the day of the race, then she would win the race. But if she wins the race, it doesn’t let us conclude that all her opponents were sick.
c
Maria could beat █ █████████ ██████ ████ ██ ███ ███████ █████
This introduces hard training as a necessary condition for beating a champion. We know that Maria beat a champion, so it must follow that she satisfied the necessary condition of training hard. (C) therefore guarantees the author’s conclusion.
d
If Sue trained █████ ███ █████ ███ ███ ████████ █████
This is irrelevant: we want to prove that Maria trained hard, not that Sue didn’t train hard.
e
Sue is usually █ ██████ ████████ █████ ████ ██████
This is irrelevant: the question is whether Maria trained hard for this race, not how generally fast she is compared to Sue.