Critical Reasoning

In 1985 the city's Fine Arts Museum sold 30,000 single-entry tickets. In 1986 the city's Folk Arts and Interior Design museums opened, and these three museums together sold over 80,000 such tickets that year. These museums were worth the cost, since more than twice as many citizens are now enjoying the arts.
Which of the following, if true, most seriously weakens the author's assertion that more than twice as many citizens are now enjoying the arts?
(A) Most visitors to one museum also visit the other two.
(B) The cost of building the museums will not be covered by revenues generated by the sale of museum tickets.
(C) As the two new museums become better known, even more citizens will visit them.
(D) The city's Fine Arts Museum did not experience a decrease in single-entry tickets sold in 1986
(E) Fewer museum entry tickets were sold in 1986 than the museum planners had hoped to sell.


OA is A but why not B

(B) The cost of building the museums will not be covered by revenues generated by the sale of museum tickets.

B cannot be the answer because the question is focused on the increase in the number of tickets. Not the costs.

A weakens the argument by saying the there might be overlap visitors. Therefore, A weakens the argument.