Answer:
B) Nuclear Warfare
Step-by-step explanation:
B) nuclear warfare is the most possible answer since both russia and Us had nuclear weapons at the time, and both countries were threatening each other. But were the cold war get hot, I personally believe nuclear warfare wouldn't have happened because of MAD -- Mutually Assured Destruction. If Russia nuclear bombed US, then it was certain that US would bomb Russia and both countries would be completely decimated so there was no point in Nuclear Warfare.