Choose the appropriate auxiliary verb:

____ you be quiet! (Order)

Correct option is D

Explanation:
The correct answer is Will.

The modal verb "will" is commonly used to give orders, commands, or strong requests in English. In the given sentence, the speaker is giving a firm instruction for someone to be quiet.
Examples of "Will" in Commands:
Will you stop making noise!
Will you sit down, please?
Will you listen to me!

Information Booster:

Use of "Will" in Commands:
Used for firm orders or strong requests.
Often seen in angry or urgent speech.
Can be softened with "please" ("Will you please stop talking?").

Other Uses of "Will":
Expressing future actions ("She will arrive soon.").
Making promises or offers ("I will help you.").
Indicating certainty ("He will pass the exam.").

Difference Between "Will" and Other Modals:
Will = Command/order ("Will you be quiet!").
Can = Request for permission ("Can you be quiet?").
Shall = Formal order ("Shall we begin?").
Must = Strong necessity ("You must be quiet.").

Additional Knowledge:

Need  – "Need" is used for necessity, not orders ("You need to be quiet.").
Might  – "Might" expresses possibility, not commands ("You might be quiet" doesn’t make sense in an order).
Ought  – "Ought" is used for moral advice, not orders ("You ought to be quiet.").