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

显示报关单所在货物的“英文品名”，对照海关编码大全，查阅商品编码，审核两者是否相符，按编码确定计量单位。