​If the Fed Desires to Weaken the Dollar Without Affecting

​If the Fed desires to weaken the dollar without affecting the dollar money supply, it should:

A) ​exchange dollars for foreign currencies, and sell some of its existing Treasury security holdings for dollars.
B) ​exchange foreign currencies for dollars, and sell some of its existing Treasury security holdings for dollars.
C) ​exchange dollars for foreign currencies, and buy existing Treasury securities with dollars.
D) ​exchange foreign currencies for dollars, and buy existing Treasury securities with dollars.