确诊儿童白血病的主要依据是（）

A.贫血、发热、出血症状明显

B.肝、脾、淋巴结肿大

C.外周血见原始细胞

D.外周血见幼稚粒细胞

E.骨髓象原始细胞增生>30%

I have been living in the United States for twenty year, but seldom _____ so lonely as now. [ ]

A. have I felt

B. I had felt

C. I have felt

D. had I felt