设=f(dfrac (x)(y),dfrac (y)(z)), f可微,则偏导数计算错误的是 () .-|||-(4分)-|||-A dfrac (partial u)(partial z)=-dfrac (y{f)_(2)'}({z)^2}-|||-B 其他选项中有正确的选项-|||-C dfrac (partial u)(partial x)=dfrac (f'')(y)-|||-D dfrac (partial u)(partial y)=-dfrac (x{f)_(1)}({y)^2}+dfrac (y{f)_(2)'}(z)