Because it provided them with guns and rum.
Answer:
Texans thought that life and property were safer within the United States than in an independent Texas. Texas was also in debt and the militia wasn't as great.
I don't know but is is an 'Officer'
A and B is out because these undoubtedly are unique Chinese achievements. So is D. The Chinese are infamous for these things. Other achievements include gunpowder, fireworks, ect.
C is basically the answer because the chinese aren't the only race or country to do so. Many people have done it in the past before them and present in the terms of civilization. It isn't simply uniquely or originally from them.