In 1961, President Kennedy took action to prevent the Soviet Union from:

A. forcing citizens to remain in East Germany.

B. forming an alliance with China.

C. establishing bases in Japan.

D. forcing West Berlin to become a part of East Germany.

What president Kennedy did in 1961 was essentially that he took action in order to prevent the Soviet Union from forcing West Berlin to become a part of East Germany - D.

He knew that the Soviet Union had appetites for increased control and rule over Berlin and Europe in general and he wanted to prevent that.