by ManhattanPrepLSAT2 Thu Sep 30, 2010 12:28 pm
We are looking for an answer that MUST be true.
We are told that Angela will get her degree once she does 2 things --
Finishes course in experimental design & finishes course on dev. psychology.
We're also told she must take experimental design before dev. psychology.
Therefore, we know for CERTAIN that if Angela has finished dev. psychology, she must have already finished experimental design, and, since she's completed both, we can conclude she will indeed earn her degree.
Note that (C) does not HAVE to be true. One way to think of whether an answer HAS to be true is to consider the alternative. The alternative for (C) would be that there ARE prerequisites for experimental design. Would that conflict with the argument? Not at all -- Angela would still need AT LEAST 2 terms to graduate (if C were true, she'd likely need more than 2). Therefore, (C) is not something that must be true.
If that got you turned around, here's a simpler argument to illustrate:
Jan wants to pack a box and toy in her suitcase. The box weighs three pounds. Therefore, the suitcase will weigh at least three pounds --
Note, we don't know, and don't need to know, anything about the weight of the toy based on this conclusion.
Similarly, since we already have all the reasoning we need to show why Angela would need at least two terms, we don't know for sure anything about the requirements (or lack thereof) for the experimental design course.
Hope that helps! Please follow up if you need further clarification.