问题
选择题
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
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。