Option C and D
8x and x^11 are monomials.
Solution:
Given, a set of expressions.
We have to find which of them are monomials.
A monomial is an expression with single term.
Now, let us check one by one options.
[tex]\text { a.) } \frac{5}{7} y^{3}+5 y^{2}+y \rightarrow \text { more than } 1 \text { term }[/tex]
[tex]\begin{array}{l}{\text { b.) } x^{2}+3 \rightarrow \text { more than one term. }} \\\\ {\text { c.) } 8 x \rightarrow 1 \text { term }} \\\\ {\text { d.) } x^{11} \rightarrow 1 \text { term }} \\\\ {\text { e.) } x^{4}+x^{2}+1 \rightarrow \text { more than one term. }} \\\\ {\text { f.) } 6 x^{2}+\frac{1}{2} y^{3} \rightarrow \text { more than one term. }}\end{array}[/tex]
Hence, option c and d are monomials.