void fun(int& a, int b, int& c) Given the function heading above, which of the function calls below are valid. Assume all variables have been declared as ints. III. fun(k, h, f); IV. fun(d, d + e, e); I. fun(d, 5, e); II. fun(d + e, 15, e); A. III only B. I only C. I and III only D. I, III and IV only E. they are all valid