Which abdominal muscles rotate the trunk to the opposite side?

The correct choice is determined by understanding how the abdominal muscles function in trunk rotation. The external oblique muscles play a crucial role in rotating the trunk. When discussing the rotation of the trunk to the opposite side, the right external oblique is specifically responsible for this movement.

When the right external oblique contracts, it facilitates the rotation of the trunk to the left side. This happens because the external obliques are positioned diagonally on the sides of the abdomen, and their contraction on one side results in rotation towards the opposite side. Thus, when you think about trunk movements, the right external oblique naturally works to generate leftward rotation.

In contrast, the left external oblique would rotate the trunk to the right, while the left and right internal obliques function differently, creating rotations to the same side as the contracting muscle. Therefore, it becomes clear that the right external oblique is the muscle actively engaged when the trunk rotates to the opposite side.