1.D 2. A 3.C 4.D
1 Is the monomial as it only contains one expression.
2. Is the difference of squares because something squared minus something squared.
3. Is standard because it is of the form
[tex]a_nx^n+ a_{n-1}x^{n-1}+...+a_1x+a_0 [/tex]
4. We know D is the not the monomial simply because its power is negative which means it does not fit the definition of a polynomial.