Which is not a polynomial?

a. 4/x^4 + 3/x^3− 2/x^2 −1

b. x^5 − 5x^4 + 4x^3 −3x^2

c. 3x^2 + 5x^4 + 2x − 12
d. x^3− 7x^2 + 9x −20

What two consecutive odd integers have a sum of -28

Which of the following represents the zeros of f(x) = 6x3 − 31x2 + 4x + 5? −5, one third , one half 5, − one third , one half 5, one third , − one half 5, one third , one half

How many sides does a regular polygon have if each exterior angle measure is 45 degrees explain your answer, i really don't understand this.