x = y++ + z++;
As in post increment operator, first the value is assigned and then it is incremented, this statement can be re-written as:
x = y + z;
y = y++;
z = z++;
So, the value of x = 10 + 12 = 22, y = 10 + 1 = 11 and z = 12 + 1 = 13.
Option (D) is correct.