Why Were American Diplomats Particularly Dismayed That the Soviets Had

Why were American diplomats particularly dismayed that the Soviets had installed a procommunist government in Poland in 1945?

A) U.S. forces had hoped to include Poland in the western European security pact that later became known at NATO.
B) The Soviet Union had ruled Poland brutally prior to the war and was responsible for most of the killings that took place there in the war.
C) Stalin had promised Winston Churchill and Franklin Roosevelt at Yalta that he would allow a democratic government in Poland.
D) Americans feared that Soviet control of Poland would make it easier for the Red Army to capture and control all of Germany.