The time the old man devotes ____ English at home is very important to him. [ ]

A. to studying

B. to study

C. of being studied

D. of studying

男，46岁，无痛性肉眼血尿1个月。查体无异常。尿中找到瘤细胞。IVP：右肾盂有一小的充盈缺损影。膀胱镜检查见右输尿管口喷血。最可靠的诊断是（）

A.肾癌

B.肾盂癌

C.肾错构瘤

D.输尿管癌

E.肾母细胞癌