Here is a question about this article: Hellenistic warfare was a continuation of the military developments of Iphicrates and Philip II of Macedon, particularly his use of the Macedonian Phalanx, a dense formation of pikemen, in conjunction with heavy companion cavalry. Armies of the Hellenistic period differed from those of the classical period in being largely made up of professional soldiers and also in their greater specialization and technical proficiency in siege warfare. Hellenistic armies were significantly larger than those of classical Greece relying increasingly on Greek mercenaries (misthophoroi; men-for-pay) and also on non-Greek soldiery such as Thracians, Galatians, Egyptians and Iranians. Some ethnic groups were known for their martial skill in a particular mode of combat and were highly sought after, including Tarantine cavalry, Cretan archers, Rhodian slingers and Thracian peltasts. This period also saw the adoption of new weapons and troop types such as Thureophoroi and the Thorakitai who used the oval Thureos shield and fought with javelins and the machaira sword. The use of heavily armored cataphracts and also horse archers was adopted by the Seleucids, Greco-Bactrians, Armenians and Pontus. The use of war elephants also became common. Seleucus received Indian war elephants from the Mauryan empire, and used them to good effect at the battle of Ipsus. He kept a core of 500 of them at Apameia. The Ptolemies used the smaller African elephant.
What is the answer to this question: From whom did Seleucus receive war elephants?
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So... Mauryan empire

Here is a question about this article: In 1875, Bell developed an acoustic telegraph and drew up a patent application for it. Since he had agreed to share U.S. profits with his investors Gardiner Hubbard and Thomas Sanders, Bell requested that an associate in Ontario, George Brown, attempt to patent it in Britain, instructing his lawyers to apply for a patent in the U.S. only after they received word from Britain (Britain would issue patents only for discoveries not previously patented elsewhere).
What is the answer to this question: What kind of telegraph did Bell create?
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So... acoustic

Here is a question about this article: The United States joined World War II in December 1941 after the Japanese attack on Pearl Harbor. On the European front, U.S. Army troops formed a significant portion of the forces that captured North Africa and Sicily, and later fought in Italy. On D-Day, June 6, 1944, and in the subsequent liberation of Europe and defeat of Nazi Germany, millions of U.S. Army troops played a central role. In the Pacific War, U.S. Army soldiers participated alongside the United States Marine Corps in capturing the Pacific Islands from Japanese control. Following the Axis surrenders in May (Germany) and August (Japan) of 1945, army troops were deployed to Japan and Germany to occupy the two defeated nations. Two years after World War II, the Army Air Forces separated from the army to become the United States Air Force in September 1947 after decades of attempting to separate. Also, in 1948, the army was desegregated by order of President Harry S. Truman.
What is the answer to this question: Which military force attacked Pearl Harbor?
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So...
Japanese