Answer: d. Countries with nuclear capabilities were able to fit nuclear weapons onto missiles that could be fired long distances.
Step-by-step explanation:
The hydrogen bomb is also referred to as a thermonuclear bomb or an H-bomb. Compared to an atomic bomb, a hydrogen bomb can be 1,000 times more potent, because it creates a greater blast, with a more extensive reach for shock waves and radiation. Furthermore, hydrogen bombs, even though they might be more difficult to build, are light enough to fit on top of a missile.