State whether the algebraic expression given below is monomial, binomial, trinomial or multinomial.

$1+x+x^2$

State whether the algebraic expression given below is monomial, binomial, trinomial or multinomial.

$7mn$

State whether the algebraic expression given below is monomial, binomial, trinomial or multinomial.

$a^2+b^2$

State whether the algebraic expression given below is monomial, binomial, trinomial or multinomial.

$100xyz$

State whether the algebraic expression given below is monomial, binomial, trinomial or multinomial.

$ax+9$

State whether the algebraic expression given below is monomial, binomial, trinomial or multinomial.

$p^2-3pq+r$

State whether the algebraic expression given below is monomial, binomial, trinomial or multinomial.

$3y^2-x^2{y}^2+4x$

State whether the algebraic expression given below is monomial, binomial, trinomial or multinomial.

$7x^2-2xy+9y^2-11$

What is the degree of following monomial?

$7y$