Select the correct passive form of the given sentence.

How many languages do you learn at school?

How many languages are being learnt by you at school?

The correct passive form of the given sentence "How many languages do you learn at school?" is How many languages are learnt by you at school?

The other options are incorrect because:

• How many languages will you learn at school? uses the future tense, while the original sentence is in the present tense.
• Languages are learnt by how many at school? is grammatically incorrect. The subject of the sentence is "languages," but the verb "learnt" is in the passive voice, which means that the subject is the recipient of the action.
• How many languages are being learnt by you at school? uses the present progressive tense, which is not typically used for actions that happen regularly.
• How many languages have you being learnt by you learning at school? is grammatically incorrect. The verb "learnt" is in the past participle form, but it is not used correctly in the passive voice.