Answer:
The first occurrence (chronologically) was
Regional kingdoms began to replace most of the city-states of the northern region of Harappan Society.
Explanation:
Of all that are stated in the question, Regional kingdoms began to replace most of the city-states of the northern region of Harappan Society first occured
Around 4,350 years ago, many factors responsible for migration led people to abandon their settlements and migrate to southern and eastern regions of India, according to a study by Indian Institute of Technology Kharagpur.
This is also known as Indus valley civilization
This is the answer for you're topic and also I got this from my old computer history so yeah.
Russia, Ukraine, Belarus, Georgia
hope this helps
