Final answer:
The Slavs are the ethnic group that emerged in Poland, Ukraine, and Belarus and went on to create modern Russia.
Step-by-step explanation:
The ethnic group that emerged in what is now Poland, Ukraine, and Belarus, and went on to create modern Russia, are called the Slavs. The Slavs are a group of Indo-European peoples who have a long history in Eastern Europe. They played a significant role in the formation of many Eastern European countries, including Russia.
Learn more about The emergence of the Slavs in Eastern Europe and their contribution to the formation of modern Russia