This limit represents the derivative of some function f at some number a. Select an appropriate f and a.

lim_(h->0) (root4(256+h)-4)/h
1
f(x) = x^4, a = 4
f(x) = x^1/4, a = 4
f(x) = x^1/4, a = 256
f(x) = √x, a = 256
f(x) = √x, a = 16