Ought to expresses moral obligation. Incorrect grammar appears in other options.

Should is primarily used to give advice or make recommendations, as in "You should try this new restaurant." Other options describe could or other modal verbs.

The Sentence  demonstrates a condition for possibility: finishing work early.

Correct answers is a polite request. The other examples use could for possibility or past ability.

The correct form is "ought to" or "ought not to," followed by a base verb. Sentence B properly uses this structure in the negative form.

Could is used here to describe an unrealized past possibility. In other answers should or ought would be more appropriate since they express advice or obligation.

Sentence B demonstrates expectation, as in predicting something likely to happen based on circumstances.

Ought requires "to" when forming questions, so "Ought you finish" is incorrect.

Should have reflects regret about a past action, as in the correct answer.

Sentence refers to past ability, a primary use of could. Other sentences use could for requests or possibilities.