Techniques that the soviet government used to control its citizens and to increase support for communism included all of the following, except
a. censorship.
c. reward and punishment.
b. terror.
d. the promotion of religion.

The Soviets are actually rather atheist - although they have a certain cooperation with ther Russian Orthodox church. But they would in any case not use religion to promote their goals - so the correct answer is:
d. the promotion of religion.  .

They uses all the other methods.