Input: 51st state
In Article 3 of the Treaty of San Francisco between the Allied Powers and Japan, which came into force in April 1952, the U.S. put the outlying islands of the Ryukyus, including the island of Okinawa—home to over 1 million Okinawans related to the Japanese—and the Bonin Islands, the Volcano Islands, and Iwo Jima into U.S. trusteeship. All these trusteeships were slowly returned to Japanese rule. Okinawa was returned on May 15, 1972, but the U.S. stations troops in the island's bases as a defense for Japan.

When was Okinawa finally returned?
Output: May 15, 1972

Input: Hydrogen
Hydrogen is commonly used in power stations as a coolant in generators due to a number of favorable properties that are a direct result of its light diatomic molecules. These include low density, low viscosity, and the highest specific heat and thermal conductivity of all gases.

Why is it used as a coolant?
Output: favorable properties that are a direct result of its light diatomic molecules

Input: Greeks
The classical period of Greek civilization covers a time spanning from the early 5th century BC to the death of Alexander the Great, in 323 BC (some authors prefer to split this period into 'Classical', from the end of the Persian wars to the end of the Peloponnesian War, and 'Fourth Century', up to the death of Alexander). It is so named because it set the standards by which Greek civilization would be judged in later eras. The Classical period is also described as the "Golden Age" of Greek civilization, and its art, philosophy, architecture and literature would be instrumental in the formation and development of Western culture.

What is so well known about this period ?
Output: It is so named because it set the standards by which Greek civilization would be judged in later eras

Input: Napoleon
Widespread rumors of Napoleon's return from St. Helena and Napoleon as an inspiration for patriotism, individual and collective liberties, and political mobilization manifested themselves in seditious materials, displaying the tricolor and rosettes. There were also subversive activities celebrating anniversaries of Napoleon's life and reign and disrupting royal celebrations—they demonstrated the prevailing and successful goal of the varied supporters of Napoleon to constantly destabilize the Bourbon regime.

Anniversaries of Napoleon's life and reign were sometimes celebrated in an effort to disrupt what?
Output:
royal celebrations