. . . . . . . is a very regular class, sir. A. My B. Mines C. Your D. Ours

The correct answer is: D. Ours

The sentence “Ours is a very regular class, sir” is a possessive sentence. It means that the class belongs to the speaker and the listener. The other options are not possessive pronouns.

• My is a first person singular possessive pronoun. It is used to refer to something that belongs to the speaker.
• Mines is a non-standard form of the possessive pronoun “mine”. It is not grammatically correct.
• Your is a second person singular or plural possessive pronoun. It is used to refer to something that belongs to the listener.

In the sentence “Ours is a very regular class, sir”, the speaker is referring to the class as something that belongs to both the speaker and the listener. Therefore, the correct pronoun to use is “ours”.