(i) Polynomial x2+ x+ 1 is a one variable polynomial, because it contains only one variable i.e., x. (ii) Polynomial y3 – 5y is a one variable polynomial, because it contains only one variable i.e., y. (iii) Polynomial xy+ yz+ zx is a three variables polynomial, because it contains three variables x, y and z. (iv) Polynomial x2 – Zxy + y2 +1 is a two variables polynomial, because it contains two variables x and y.