在xR²⁺ + yH⁺ +O₂ = mR³⁺ + nH₂O的离子方程式中,对化学计量数m 和R²⁺、R³⁺判断正确的是

A．m="y," R^3+是还原剂	B．m="2y," R^2+被氧化
C．m="2," R^3+是氧化剂	D．m="4," R^2+是还原剂