GMAT Critical Reasoning (CR) | The vast majority of countries that have a single political party

Political theorist: The vast majority of countries
that have a single political party have corrupt
national governments, but some countries
with a plurality of parties also have corrupt
national governments.What all countries with
corrupt national governments have in
common, however, is the weakness of local
governments.

If all of the political theorist’s statements are true,
which one of the following must also be true?

(A) Every country with weak local government has
a single political party.
(B)
...

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