The function f(r) = ag +a lrl+azlæ|+aglz is differentiable at r =0 (a) for no values of ag, a1,a2 a3 (b) for any value of ag, a1,a2, 3. (c) only if a = 0. (d) o

The function f(r) = ag +a lrl+azlæ|+aglz is differentiable at r =0 (A) for no values of ag, a1,a2 a3 (B) for any value of ag, a1,a2, 3. (C) only if a = 0. (D) only if both a =0 and ag = 0.