Commentator: The theory oftrade retaliation states thatcountries closed outof any ofanother country’s
markets should close some oftheir own markets to the other country in order to pressure the other country to
reopen its markets. If every country acted according to this theory, no country would trade with anyother.
The commentator’s argument relies on which of the following assumptions?
(A) No country actually acts according to the theory of trade retaliation.
(B) No country should block any of its markets to foreign trade.
(C) Trade disputes should be settled by international tribunal.
(D) For any two countries, at least one has some market closed to the other.
(E) Countries close their markets to foreigners to protect domestic producers.

I picked A by negation. Doesn’t negating A break the argument ?