I have been living in the United States for 20 years but seldom so lonely as now.A. hav

问题补充：

I have been living in the United States for 20 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：A考查倒装和时态。句意：我在美国生活了，但是很少像现在这样感到如此孤独。否定词seldom置于句首，句子要用部分倒装，再根据前面的“have been living”可知此处应用现在完成时。故选A项。