During the past 1000 years there were at least glacial periods. 4
20
12
60

Explanation:

《●●●●●■■■■■♤♤♤◇◇The Last Glacial Period (LGP) occurred from the end of the Eemian to the end of the Younger Dryas, encompassing the period c. 115,000 – c. 11,700 years ago. This most recent glacial period is part of a larger pattern of glacial and interglacial periods known as the Quaternary glaciation extending from c. 2,588,000 years ago to present.[1] The definition of the Quaternary as beginning 2.58 Ma is based on the formation of the Arctic ice cap. The Antarctic ice sheet began to form earlier, at about 34 Ma, in the mid-Cenozoic (Eocene–Oligocene extinction event). The term Late Cenozoic Ice Age is used to include this early phase.[2]●●●●●■■■■■♤♤♤♤♤◇◇◇》

answer; ///i do believe that the correct answer is (d); ///athens had a small population;

d

explanation: