What is the transformation of the regret expressed in wishing for past actions?

The phrase "If only I had studied harder" captures the essence of expressing regret about a past action, specifically referring to a situation that cannot be changed since it already occurred. This structure uses the past perfect tense "had studied," indicating that the speaker is reflecting on a decision made in the past and wishing it had been different.

In contrast, other options either use the present tense or imply a future condition, which does not convey the idea of regret about a past action. The present tense options, such as "If only I studied harder" and "If only I study harder," suggest a hypothetical scenario in the present or future rather than reflecting on something that has already happened. The phrase "If only I would have studied harder" is also incorrect because it combines "would" with the perfect aspect in a way that is not standard in English, resulting in a grammatically awkward construction.

Thus, the correct answer effectively communicates a wish regarding a past action, emphasizing the remorse and desire for a different outcome.