Calculate the derivative of y = Vx+ Vx . . . ... If the Chain Rule only needs to be used once, which functions should be used? If it must be used more than once, which functions should be used the first time? O A. g(x) = Vx and f(u) = Vu O B. g(x) = x + Vx and f(u) = Vu O C. g(x) =x + Vx and f(u) = u O D. g(x) = Vx and f(u) = u + vu