The answer is:
A.they had no interest in European manufactured goods
The emperors believe that letting manufactured goods conquered Chinese market would increase foreign influence in Chinese's government.
D.they pursued a policy isolationism
This mean that China would not take sides whenever other countries are involved in a conflict with one another,
E.they limited trade to one port
Limiting trade to one port make it easier for the government to monitor the goods that come in and out of Chinese's territory. This would prevent foreign countries from smuggling their products into the country,