The CIA participated in the Cold War by

Ahelping design efficient weapons systems.
Bcarrying out secret operations in other countries.
Cspying on the Soviet Union.
Dhelping the president determine foreign policy.

Verified Answer :

The CIA participated in the Cold War mostly by "B. carrying out secret operations in other countries," since these covert operations were crucial in order to gather intelligence and "take out" certain threats. 

carrying out secret operations in other countries.