The expression -3h⁴ + 7(h - 1) is a

1. monomial
2. binomial
3. trinomial
4. none of these

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