Which of the following is a pair of like terms?

1. ab, xy

2. 2xz², -7x²z

3. 4a²b², -$\dfrac{1}{3}$a²bc

4. 0.9 xy, - $\dfrac{2}{11}$ xy

The degree of the polynomial ma²b³ + 6ab² - m is

1. 6
2. 5
3. 3
4. 2

Which of the following is a binomial?

1. a² - 6b² + 1000
2. -7x²y + xy² + 3x²y
3. ma²b - (m + n)a²b² + nab²
4. st² - st + 1

Which of the following is a polynomial?

1. $x - \dfrac{1}{x}$

2. $x + \sqrt{x}$

3. $\dfrac{x}{\sqrt{2}} - \dfrac{1}{\sqrt[3]{2}}$

4. $x^{\dfrac{1}{2}} + x^{\dfrac{-1}{2}}$