Which heading best completes this partial outlines a natural boundaries of desert, mountains, and the sea yearly fluding to enrige farm land \ old or middle kingdom production of peyprus plant

Why did poland, hungary, and east germany join the warsaw pact? a)their people voted to join in free elections. b)their efforts to join nato failed. c)they wanted to stop the spread of communism in europe. d)they were soviet satellites that had little choice.