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

Aforcing citizens to remain in East Germany.
Bforming an alliance with China.
Cestablishing bases in Japan.
Dforcing West Berlin to become a part of East Germany.

Verified Answer :

The answer is D. forcing West Berlin to become a
part of East Germany. When the Russians built the Berlin Wall, people in
the East were desperate to leave to leave and go to the West.  The West was also disappointed with Kennedy
because the Wall was not only hard to cross but Communists now threatened
them.  Kennedy reaffirmed his support by
Sending Vice President Lyndon Johnson and U.S. troops to reaffirm his
commitment to the West.

Neuron

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.