This question tests your understanding of modal auxiliaries in English grammar. Modal auxiliaries are special verbs (like can, could, may, might, must, shall, should, will, would, ought to) that are used with other verbs to express ability, possibility, permission, or obligation.

The sentence is: "You ___ pay your taxes."

Let's analyze the meaning. Paying taxes is not just a possibility or an ability; it is a legal and moral obligation. It is something that is required by law.

Now, let's evaluate the options:

Might and May are used to express possibility or permission (e.g., "It might rain," "You may leave"). They do not convey a strong sense of obligation.

Can is used to express ability or permission (e.g., "I can swim," "You can go now"). It also does not convey obligation.

Ought to is used to express moral obligation or strong recommendation (e.g., "You ought to help your friends"). It is the perfect fit for a sentence about a duty like paying taxes.

While "must" would also be a very strong and correct choice for obligation, it is not one of the given options. Among the choices provided, "ought to" is the only one that correctly conveys the sense of duty and obligation required by the sentence.

Final Answer: You ought to pay your taxes.

Related Topic: Modal Auxiliaries

Modal verbs are defective verbs; they do not have all the regular tenses and forms. Their primary function is to modify the main verb in a sentence to express a specific mood or attitude, such as:

• Obligation/Duty: must, ought to, should
• Possibility/Permission: may, might, can, could
• Ability: can, could
• Advice/Suggestion: should, ought to

Key Formula/Theory

The structure for using a modal auxiliary is always: $\text{Subject}+\text{Modal}+\text{Base Verb}$
The main verb that follows the modal must always be in its base form (the infinitive without "to"). The exception is the semi-modal "ought to," which is followed by the base verb but includes the word "to".

Example: She can speak French. | You ought to help.