What was donated by King Attalus II?

King Attalus II is best known for his contribution to the cultural and architectural heritage of Athens through the donation of the Stoa of Attalus II. This structure, built in the 2nd century BCE, served multiple purposes, including as a marketplace and a place for public gatherings. The Stoa exemplifies the architectural style of the Hellenistic period with its elegant colonnades and practical design.

Additionally, the Stoa of Attalus II was significant in that it not only reflected the political philanthropy of its donor but also acted as a symbol of the connection between Athens and the Attalid dynasty. This building was later reconstructed and houses the Museum of the Ancient Agora today, further emphasizing its historical importance.

The other options listed, such as the Temple of Apollo Epikourios, the Erechtheion, and the Theater of Epidauros, are significant architectural landmarks but are not attributed to King Attalus II's donation. Each of these other structures has its own unique historical background and significance, distinct from the contributions made by Attalus II.