For C++

Given the prototype:

int f(int, int &);

and the variable declarations:

short x = 10;

long y = 100000;

int z = 15;

Which of the following are valid calls to f?

a. x = f(x, y);

b. x = f(y, z);

c. x = f(2,3);

d. both a and b

e. all are correct