Classify the following polynomials as monomials, binomials, trinomials. Which polynomials do not fit in any of these three categories `x + y, 1000, x + x^2 + x^3 + x^4, 7 + y + 5x, 2y – 3y^2, 2y – 3y^2 + 4y^3, 5x – 4y + 3xy, 4z – 15z^2, ab + bc + cd + da, pqr, p^2q + pq^2, 2p + 2q`