The monomials, binomials, trinomials and quadrinomials are as follows.
(i) a2 is a monomial expression as it contains one term only.
(ii) a2 - b2 is a binomial expression as it contains two terms.
(iii) x3 + y3 + z3 is a trinomial expression as it contains three terms.
(iv) x3 + y3 + z3 + xyz is a quadrinomial expression as it contains four terms.
(v) 7 + 5 = 12 is a monomial expression as it contains one term only.
(vi) abc +1 is a binomial expression as it contains two terms.
(vii) 3x - 2 + 5 = 3x + 3 is a binomial expression as it contains two terms.
(viii) 2x - 3y + 4 is a trinomial expression as it contains three terms.
(ix) xy + yz + zx is a trinomial expression as it contains three terms.
(x) ax3 +bx2 +cx + d is a quadrinomial expression as it contains four terms.