Which of the expressions below is/are polynomials?

I. [tex]-2x^{5}-3x^3+5x^2-2x+4[/tex]
II. [tex]\frac{3}{4}[/tex][tex]x^4-3x^3+x-4[/tex]
III. [tex]3x^2-2\sqrt[3]{x^2}[/tex]

a. I and III
b. II and III
c. II and III
d. I,II and III