A. x
B. y and z
C. x, y and z
D. Neither x, nor y, nor z

Solution

C. x, y and z

Explanation

In the code shown above, x, y and z are global variables inside the function f. y and z are global because they are not assigned in the function. x is a global variable because it is explicitly specified so in the code. Hence, x, y and z are global variables.