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Must Be True—Formal Logic. The correct answer choice is (B)
The stimulus does not contain a conclusion and can be diagramed as follows:
SP = counties with a single political party
P = countries with a plurality of parties
CG = corrupt national governments
WLG = weakness of local governments
The diagram yields two inferences:
Given that the question stem is a Must Be True, you should look for an answer choice that contains
one of the two inferences. Answer choice (B) contains the second inference and is correct.
Answer choice (A): This answer contains two errors, both of which are fatal: first, it attempts to
reverse the chain between the single party and weak local governments and second it tries to change
a most statement into an all statement.
Answer choice (B): This is the correct answer. The answer can be a bit tricky to spot since the
statement is reversible, and the wording of the answer is given from the reversed perspective. This
is a common trick used by the test makers, and you should be prepared for it when solving Formal
Answer choice (C): Although this answer could be true, it does not have to be true. From the inherent
inference of the statement contained in the last sentence of the stimulus, we can conclude that some
countries with weak local governments do have corrupt governments, and thus it is possible that all
countries with weak local governments have corrupt governments.
Answer choice (D): This answer choice improperly reverses the first inference.
Answer choice (E): The stimulus does not provide information as to the total number of countries
with single political parties or a plurality of parties. Thus, the statement in this answer choice cannot
be proven true. Remember, the most and some statements in the stimulus relate to different entities,
hence no comparative inference can be drawn. The following example shows why this answer is