I did not understand the explanation in the video.
I diagrammed the following based on my understanding.
ES and PIL ---> OS
PIL ---> OS/e
Therefore, /E and PIL
I chose answer choice A thinking the only part that is missing from the premise to the conclusion is ES---> OS.
http://7sage.com/lsat_explanations/lsat-61-section-2-question-03/
Comments
The argument begins with a pretty standard conditional statement:
(Economic success AND Protecting individual liberty success)----->Overall success.
Then, we are given a quasi-conditional statement: We can't diagram this statement because we don't know if Protecting individual liberties actually is a sufficient condition for success. All we know is that is "may" be a success.
Also, the part of about the environment is irrelevant because it isn't apart of any conditional chain. Think of it as this: Despite not caring for the environment, political administrations can be successes if they protect individual liberties. The "environmental" idea is a complete side thought.
The last sentence is baiting you think that the environmental stuff is relevant, but since we know it isn't now, you can ignore that part. Thus, the relevant parts of the final sentence are this: we have successfully protected individual liberties.
Since this is a must be true question, and we only have one true conditional statement (and one of the two sufficient conditions satisfied), I am going to bet the correct answer is: "If we have economic success as well, then we are an overall success." This is what answer choice C says. It must be true given our conditional statement and what we know about the matter.
Answer A is incorrect because it only gets us half way there. Why must it be true that we are economically successful? We no indication that we are. Notice that compared to answer choice C, C gives us an "IF" we are economically successful, which isn't as absolute of a statement as answer choice A.