Select the correct passive form of the given sentence.
How many languages do you learn at school?

Correct option is C

The correct active/passive voice of the given sentence is (c).
Active voice: The subject performs the action.
Passive voice: The action is performed on the subject. The given sentence is in Simple Present Tense (Interrogative form), starting with "How many languages" which is the object in the sentence.

In the Simple Present Tense, passive voice is formed as:
Object + is/are/am + past participle (V3) + by + subject
The sentence is an interrogative one with a "Wh-" question word (How many), which must remain at the start of the sentence in passive voice as well.
Step-by-step conversion:
Active Sentence: How many languages do you learn at school?
Identify subject: you
Identify verb: learn (present tense, base form)
Identify object: languages (plural noun)
Since "languages" is plural, we use are in passive voice.
Past participle of "learn" is "learnt" (both "learned" and "learnt" are correct; "learnt" is often preferred in British English).
Place by you at the correct position.
Thus, the correct passive form:
How many languages are learnt by you at school?
Structure Used:
Active Voice (Interrogative - Wh-word):
Wh-word + do/does + subject + base verb + object?
Passive Voice (Interrogative - Wh-word):
Wh-word + is/are + past participle (V3) + by + subject?