I have been living in the United States for twenty years but seldom so lonely as now.A.

问题补充：

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

答案：

(答案→)A. have I felt

B. I had felt

C. I have felt

D. had I felt

解析：本题考查倒装结构。句中否定词seldom放在句首，故用倒装结构，根据时态用现在完成时。句意：我在美国生活了了，但我很少像现在一样孤独。