In mathematics, the term "monomial" is used to refer to an algebraic expression that contains only one term.
Monomials can either be:
1- numbers (example: 2, 27,...etc)
2- numbers and variables multiplied together (example: 7xy , 33x,.....etc)
3- variables multiplied together (example: xy, abc, ....etc)
Based on the above explanation, we will find that the choice that fits the definition of monomial is:
the first choice: 12c