How did communication improve during the Qin dynasty? O A standardized writing system was created.
O An organized postal system was established.
O A new system of military message codes was developed.
A ban against criticizing the government was passed.

During the Qin Dynasty, paper began to be invented and the writing system of China was standardized.

Explanation:

link

the two atomic bombs dropped on japan in 1945 killed and maimed hundreds of thousands of people, and their effects are still being felt today. the uranium bomb detonated over hiroshima on 6 august 1945 had an explosive yield equal to 15,000 tonnes of tnt.