Which of the following is the limit definition of fu (a, b)? C f(a, b t h) - f(a, b) lim h-0 h O fa, y th) - f(a, y) lim y -ta h O f(a + h, b) - f(a, b) lim h-0 h O f (a, b) th - f(a, b) lim h-+0 h O f(a, y th) - f(a, b) lim y -> a h