No nation can long survive unless its people are united by a common tongue. For proof, we need only consider Canada, which is being torn asunder by conflicts between French-speaking Quebec and the other provinces, which are dominated by English speakers.
Which of the following, if true, most effectively challenges the author’s conclusion?
(A) Conflicts over language have led to violent clashes between the Basque-speaking minority in Spain and the Spanish-speaking majority.
(B) Proposals to declare English the official language of the United States have met with resistance from members of Hispanic and other minority groups.
(C) Economic and political differences, along with linguistic ones, have contributed to the provincial conflicts in Canada.
(D) The public of India, in existence sine 1948, has a population that speaks hundreds of different, though related, languages.
(E) Switzerland has survived for nearly a thousand years as a home for speakers of three different languages.
Confused as to why the right answer is actually the right one. Will post the OA after a few replies

Agree with beckee529.
nation can survive if people don't speak a common language.
because Canada as conflicts between French and Eng speaking people.
The Questions stems asks us to weaken the authors argument.
a) If we can find another reason for conflicts in Canada.
b) If we can give eg of another country which is surviving in spite of multiple languages.
A - Out of scope.
. So in a way strengthens the authors argument.
D - Can't say.. May be India also might be having similar conflicts due to language .. We cannot assume things in GMAT.
E - Correct. Weakens the author properly.