Under the Bretton Woods System,each Country Was Responsible for Maintaining $\pm$

Under the Bretton Woods system,each country was responsible for maintaining its exchange rate within $\pm$ 1 percent of the adopted par value by

A) buying or selling foreign exchanges as necessary.
B) buying or selling gold as necessary.
C) expanding or contracting the supply of loanable funds as necessary.
D) increasing or decreasing their money supply as necessary.