窦道的主要发病机制是（）
A.手术创伤
B.残留异物
C.腐肉不除
D.余邪未尽
E.正气内虚
参考答案：D
I have been living in the United States for twenty years, but seldom ___ so lonely as now. [ ]
A. have I felt
B. I had felt
C. I have felt
D. had I felt
一个小数的小数点向左移动两位，所得到的新数比原数小3.564。原数是多少？
