Answer: a.the “ziggurats” were built as temples for the Sumerian gods.
The main reason ancient Mesopotamians built ziggurats in 2000 B.C is due to their religious belief that if they build temples, the heaven and the earth will be connected and therefore they will be closer to the gods. Ziggurats were made of mud-brick or cut sandstone blocks and were usually built near houses so people can get to the temple and leave offerings to the gods easily.
