Answer:
Correct options are:
1.No learning occurred.
2.People forgot or lost skills that the Greeks and Romans had developed.
3.Society was more violent because there was no central government.
Step-by-step explanation:
Only the last option is not correct as most of the people didn't know how to read and write. Even the rulers were often unable to read and write. Monasteries were the centers of education for a long period.
Therefore all other options are correct as people lost most of educational skills, had no scientific knowledge, and the lack of centralized government made large problems for the society in general.