Question

Besides isolationism, what is another reason why Imperial China limited trade?

Europeans valued their goods at much higher than their actual worth.
China wanted to prevent its ports from being polluted by foreign ships.
China feared Christian evangelism was harming Confucian tradition.
Europeans continued to produce porcelain, tea, and silk in excess.

Answer 1

China feared Christian evangelism was harming Confucian tradition.

Officials saw missionary activity as a threat to social order and Confucian ritual practice, so the Ming/Qing limited foreign contact and trade as part of controlling foreign influence (including Christianity).