What does "I regret not visiting my grandmother last week" express?

The statement "I regret not visiting my grandmother last week" conveys a feeling of remorse or disappointment about an action that did not happen—in this case, the visit to the grandmother. By expressing regret, the speaker is indicating a desire for a different outcome, specifically wishing that they had made the choice to visit. This aligns perfectly with the idea presented in the correct answer, which clearly articulates the wish to have taken a different action.

The expression of regret inherently communicates that the speaker reflects on the past and acknowledges a missed opportunity, suggesting a desire to change that experience if given the chance. Thus, the choice that states, "I wish I had visited my grandmother," encapsulates this sentiment accurately.