The political economy of many of the world's nation-states has changed radically since the late 1980s. Which of the following is a trend that has been evident?

A、a wave of democratic revolutions has swept the world.
B、totalitarian governments have arisen, replacing democratically elected governments.
C、there has been a strong move toward centrally planned economies and away from free market economic models.
D、mixed economies are fast replacing market economies.