Answer:
Option B,

Explanation:
Given:
m(x)=2√x
m(n(x))=18√x^3
To find the expression for n(x), we need to determine the relationship between m(x) and n(x) from the given information.
Substitute m(x) into the equation m(n(x))=18√x^3 and solve for n(x).

Thus, option B is correct.