Mark Twain wrote about the _____people because he knew them well

Mark Twain wrote about the _____people because he knew them well and their life was the one he himself had lived.
A、lower-class
B、middle-class
C、upper-middle-class
D、upper-class
【正确答案】：A
【题目解析】：马克·吐温写下层社会的人，因为他很了解他们，他们的生活和他自己一样。