(2)已知 =V(x,y,z)=dfrac ({x)^2}({a)^2}+dfrac ({y)^2}({b)^2}+dfrac ({z)^2}({c)^2}, 则 gradV=() .-|||-A. (dfrac (2x)({a)^2},dfrac (2y)({b)^2},dfrac (2z)({c)^2}) B. sqrt (dfrac {4{x)^2}({a)^4}+dfrac (4{y)^2}({b)^4}+dfrac (4{z)^2}({c)^2}}-|||-C.(2x,2y,2z ) D. (dfrac (1)({a)^2},dfrac (1)({b)^2},dfrac (1)({c)^2})