Canada has to work with the United Sates to solve the problem of acid rain because

Canada has to work with the United Sates to solve the problem of acid rain because the United States A.
Is the source of much of Canada's air pollution

B.
Purchases many of the goods that Canada produces in its factories

C.
Has reduced the amounts of acid rain and understands how to solve the problems

D.
Is careful to keep air pollution from leaving the United States and entering Canada