Give an example of a polynomial,which is:
$(i)$ monomial of degree $1$
$(ii)$ binomial of degree $20$
$(iii)$ trinomial of degree $2$

(N/A) polynomial having only one term is called a monomial,a polynomial having only two terms is called a binomial,and a polynomial having only three terms is called a trinomial.
$(i)$ $3x$ is a monomial of degree $1$.
$(ii)$ $x^{20} - 7$ is a binomial of degree $20$.
$(iii)$ $5x^2 + 3x - 1$ is a trinomial of degree $2$.