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:考查倒装句。否定词放在句首,使用部分倒装,题中的否定词为seldom,根据时态应用完成时态,所以助动词have 提前,选A。