단항식과 다항식의 계산

Determine whether each polynomial is a monomial, binomial, trinomial, or other polynomial.

• ⓐ $\,z$
• ⓑ $\,2{x}^{3}-4{x}^{2}-x-8$
• ⓒ $\,6{x}^{2}-4x+1$
• ⓓ $\,9-4{y}^{2}$
• ⓔ $\,3{x}^{7}$