This refers to the earliest complex societies that were centered around the nile, tigris, euphrates, indus, and huang he areas.

River valley civilizations

Explanation:

They were centred around various river valleys as their main source of livelihood and the flourished only due tiote river valley on which they were based. Like the harappan in Indus Valley, The yellow river (Huang He), the Mesopotamia around Tigris and Euphrates and the egyptian Nile.

answer; ///(true)/// fusion occurs in the sun's core;