C. a historian could use this source to learn more about what the chinese though about foreigners. d. a historian could use this source to learn more about the chinese christian community.

B. A historian could use the source to learn more about how foreigners traveled in China at this time.

Explanation:

also I have a question did u mean 'thought' instead of 'though'?

necessary and proper clause. the congress shall have power to all laws which shall be necessary and proper for carrying into execution the foregoing powers, and all other powers vested by this constitution in the government of the united states, or in any department or officer thereof.