Let $\mathrm{U}$ Be the Smallest Possible Universal Set That Includes All of All

Let $\mathrm{U}$ be the smallest possible universal set that includes all of the crops listed; and let $\mathrm{A}, \mathrm{K}$ , and $\mathrm{L}$ be the sets of five crops in Alabama, Arkansas, and Louisiana, respectively. Find the indicated set.
-L' $\cap$ A

A) $\{c, s\}$
B) $\{\mathrm{h}, \mathrm{n}, \mathrm{t}, \mathrm{w}\}$
C) $\{n, r, t\}$
D) $\{\mathrm{h}, \mathrm{p}, \mathrm{w}\}$