Explanation:
Answer:
The correct options are C and D.
Explanation:
Monomial: A monomial is an algebraic expression that contains one term. The Monomials includes numbers, whole numbers and variables that are multiplied together, and variables that are multiplied together.
For example:  are monomials.
All the options contains more than one term except C and D.
In option C, the given expression is

Since it contains only one term, therefore It is a monomial.
In option D, the given expression is

Since it contains only one term, therefore It is a monomial.
Option C and D are correct.