i have been living in the United States for twenty years

问题描述:

i have been living in the United States for twenty years
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
我xuanD,他不是现在孤独吗,那之前不就是过去

是啊,他是现在觉得孤独,所以用现在完成时,还有前面一句用的也是现在完成进行时,前后两句时态应该一致.如果选D,表示过去的过去,过去完成时.