Jim is a ____ boy, and today is his _____ birthday.

A．twelve-years-old, twelve

B．twelve-years-old, twelfth

C．twelve-year-old, twelve

D．twelve-year-old, twelfth

表示HRP纯度（RZ）的是（）

A.λ275nm/λ403nm

B.λ403nm/λ275nm

C.λ290nm/λ275nm

D.λ420nm/λ275nm

E.λ403nm/λ290nm