During the early middle ages in europe a. cities increased in size. b. trade with areas outside of europe increased. c. warfare frequently occurred. d. population increased.

In the European history, the Early Middle ages lasted from 5th to the 10th century. The Early Middle Ages was the period where population was declining, majority of which was from the urban centers. The trades were also decreasing, increasing the immigration. From this statement, D, B, A can be cancelled out. 

Treated as a slave is cruel and harsh