5. Given the rectangular prism $A B C D-\Lambda^{\prime} B^{\prime} C^{\prime} D^{\prime}$, among the following twelve lines: $A B^{\prime}, B A^{\prime}, C D^{\prime}$, $D C^{\prime}, A D^{\prime}, D A^{\prime}, B C^{\prime}, C B^{\prime}, A C, B D, A^{\prime} C^{\prime}, B^{\prime} D^{\prime}$, how many pairs of skew lines are there?
(A) 30 pairs
(B) 60 pairs
(C) 24 pairs
(D) 48 pairs
5.【Analysis and Solution】The given 12 lines are the diagonals on each face of the rectangular prism $A B C D-A^{\prime} B^{\prime} C^{\prime} D^{\prime}$. Taking the line $A B^{\prime}$ as an example, the intersecting diagonals are $A C, A D^{\prime}, B^{\prime} D^{\prime}, B^{\prime} C, A^{\prime} B$, and the parallel diagonals are $D C^{\prime}$. Therefore, there are 5 skew diagonals to $A B^{\prime}$: $C D^{\prime}, A^{\prime} C^{\prime}, B D, B C^{\prime}, A^{\prime} D$. Generally, for each diagonal on the faces of the rectangular prism, there are five diagonals on the other five faces that are skew to it. Thus, the 12 diagonals form 60 pairs of skew diagonals (with repeated counts). However, in the above counting, each pair of skew lines is counted twice, so there are only 30 pairs of skew lines.