In the following question, a sentence has been given in Active voice. Out of the four alternatives suggested, select the one which best expresses the same sentence in Passive voice: Who taught you to ride?

Introduction / Context:
This item tests your ability to convert a question from Active to Passive voice while maintaining correct tense, word order, and sense. The active sentence is "Who taught you to ride?" The task is to rephrase it in Passive voice in a natural, grammatically accurate way, using typical interrogative structure for the passive form.

Given Data / Assumptions:

• Active sentence: "Who taught you to ride?"
• Subject in active: "Who" (the unknown agent).
• Object in active: "you".
• Main verb: "taught" (simple past of "teach").
• We need a passive question where "you" becomes the subject.
• The correct tense in the passive will be "were taught".

Concept / Approach:
In converting from Active to Passive voice, the object of the active sentence becomes the subject of the passive one, and the subject of the active sentence may be expressed as an agent with "by" if needed. For questions, we also have to preserve the question word and proper auxiliary inversion. The active "Who taught you to ride?" becomes in passive "By whom were you taught to ride?" Here, "you" has moved to subject position, the auxiliary "were" plus past participle "taught" carry the tense, and "Who" turns into the object of the preposition "by whom". This is a standard bookish passive question pattern in formal English.

Step-by-Step Solution:
Step 1: Identify object and verb: object "you", verb "taught", time simple past. Step 2: In passive, begin with the new subject "you", but because this is a question about the agent, we use "By whom" at the beginning. Step 3: Keep the tense as past simple, so use "were taught" for a second person singular subject: "you were taught". Step 4: Place the auxiliary "were" before the subject to form a question: "were you taught". Combined with the question phrase, this gives "By whom were you taught". Step 5: Attach the infinitive phrase "to ride" unchanged at the end. Step 6: Final passive form: "By whom were you taught to ride?" Step 7: Compare this with the options to find the exact match.

Verification / Alternative check:
We can match structure with other examples: Active "Who helped you?" becomes Passive "By whom were you helped?" Similarly, "Who praised her?" becomes "By whom was she praised?" Both follow the pattern "By whom was or were subject past participle". Our passive sentence "By whom were you taught to ride?" follows this exact pattern and therefore is correct. Reading it aloud also confirms that it is a natural formal passive question.

Why Other Options Are Wrong:
"By whom is you taught to ride?" uses "is" instead of "were", changing the tense to present and also misapplying "is" to the subject "you". "Riding by you was taught by who?" is clumsy and unnatural; it changes the focus and fails to keep the interrogative structure. "Riding by you was taught by whom?" is still awkward and does not sound like standard English; it also does not remain a direct question. Any form that does not begin with "By whom" plus properly inverted auxiliary "were you taught" fails to accurately convey the active question in passive voice.

Common Pitfalls:
Students sometimes incorrectly keep "who" at the beginning in passive form, producing unidiomatic sentences like "Who were you taught by?", or they forget to adjust the tense and auxiliary for the passive. Others forget that in formal written style, "by whom" is preferred over "who by". To avoid these errors, always identify the active verb's tense first, form the passive verb phrase with the correct form of "be" and the past participle, and then place "by whom" at the start for questions about the agent.

Final Answer:
The correct passive form of "Who taught you to ride?" is By whom were you taught to ride?