In 334 BC, Alexander the Great invaded the Achaemenid Empire, defeating the last Achaemenid emperor, Darius III, at the Battle of Issus. Following the premature death of Alexander, Iran came under the control of the Hellenistic Seleucid Empire. In the middle of the 2nd century BC, the Parthian Empire rose to become the main power in Iran, and the century-long geopolitical arch-rivalry between Romans and Parthians began, culminating in the Roman–Parthian Wars. The Parthian Empire continued as a feudal monarchy for nearly five centuries, until 224 CE, when it was succeeded by the Sassanid Empire. Together with their neighboring arch-rival, the Roman-Byzantines, they made up the world's two most dominant powers at the time, for over four centuries.
Who was the last Archaemenid Emperor at the time of its defeat by Alexander the Great?
Darius III

Meleager and the infantry supported the candidacy of Alexander's half-brother, Philip Arrhidaeus, while Perdiccas, the leading cavalry commander, supported waiting until the birth of Alexander's unborn child by Roxana. After the infantry stormed the palace of Babylon, a compromise was arranged – Arrhidaeus (as Philip III) should become king, and should rule jointly with Roxana's child, assuming that it was a boy (as it was, becoming Alexander IV). Perdiccas himself would become regent (epimeletes) of the empire, and Meleager his lieutenant. Soon, however, Perdiccas had Meleager and the other infantry leaders murdered, and assumed full control. The generals who had supported Perdiccas were rewarded in the partition of Babylon by becoming satraps of the various parts of the empire, but Perdiccas' position was shaky, because, as Arrian writes, "everyone was suspicious of him, and he of them".
Who documented that Perdiccas' was under suspicion? 
Arrian

The 2015 Human Development Report by the United Nations Development Program was released on December 14, 2015, and calculates HDI values based on estimates for 2014. Below is the list of the "very high human development" countries:
On what date was the 2015 Human Development Report released?
December 14, 2015