单项选择题

A.9-(2-羟乙氧基甲基)鸟嘌呤
B.9-(2-羟丙氧甲基)鸟嘌呤
C.9-(2-羟甲氧基甲基)鸟嘌呤
D.9-(2-羟乙氧基丙基)鸟嘌呤
E.9-(2-羟丙氧基甲基)鸟嘌呤