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
网友回答
(答案→)A. have I felt
B. I had felt
C. I have felt
D. had I felt
解析：句意：我在美国已经住了20年了，但很少像现在这样孤独。由seldom 可知需要使用部分倒装结构，同时我们不难判断应使用现在时态。