Let $U=\{19,20,21,22,23,24,25\}$ and $A=\{19,23,24,25\}$. Find $A^{\prime}$. Select the correct choice below and, if necessary, fill in the answer box to complete your answer. A. $A^{\prime}=\{\}$ (Use a comma to separate answers as needed.) B. $A^{\prime}$ is the empty set.

Step 1 ：Let the universal set \(U = \{19, 20, 21, 22, 23, 24, 25\}\) and the set \(A = \{19, 23, 24, 25\}\).

Step 2 ：The question is asking for the complement of set A in U. The complement of a set A, denoted by \(A^\prime\), is the set of all elements in the universal set U that are not in A.

Step 3 ：So, we need to find all the elements in U that are not in A.

Step 4 ：\(U = \{19, 20, 21, 22, 23, 24, 25\}\)

Step 5 ：\(A = \{19, 23, 24, 25\}\)

Step 6 ：\(A^\prime = \{20, 21, 22\}\)

Step 7 ：Final Answer: \(A^\prime = \boxed{\{20, 21, 22\}}\)