Question

The development of an atomic bomb by the United States did which of these?

pressured German leaders to surrender

increased tensions between Truman and Stalin

worried the leaders of France and Great Britain

led Stalin to postpone a Soviet invasion of Japan

Answer 1

I'd likely go with that it increased tensions between Truman and Stalin.

Stalin already had his suspicions about the West -- despite being "allies", he never completely trusted them -- and the atomic bomb program's secrecy only added more proof that they weren't being completely up front even though he likely already knew about it through spies

It didn't pressure the Germans to surrender -- they had no choice but to do that when the Allies crushed them. And it didn't necessarily worry France or Britain. Britain actually ran its own a-bomb program, but the US quickly sped ahead because of its resources and manpower.

It also didn't necessarily keep Stalin's mitts off of Japan. The Soviets were ready to invade and had already proven willing to engage the Japanese at Manchukuo and Sakhalin. Instead, some debate that the bomb was also used to prevent an invasion by ending the war quickly and prevent Stalin from gobbling up territory as he did in Eastern Europe.