In the following question on voice, choose the option that expresses the sentence "The tutor always answers the questions of the students" in the passive voice.

Introduction / Context:
This question examines understanding of the transformation between active voice and passive voice in English grammar. The original sentence is in the active voice with a clear subject, verb, and object. The task is to rewrite it in the passive voice while preserving both the meaning and the tense, and while maintaining correct subject–verb agreement.

Given Data / Assumptions:
- Active sentence: “The tutor always answers the questions of the students.” - Subject: “The tutor”. - Object: “the questions of the students”. - Verb: “answers”, in the simple present tense. - Adverb of frequency: “always”.

Concept / Approach:
To change an active sentence to the passive voice, the object of the active sentence becomes the subject of the passive sentence. The main verb is rewritten using an appropriate form of “to be” plus the past participle. The original subject is often introduced by the preposition “by”. In the simple present tense, plural subjects take “are” as the auxiliary verb. Adverbs such as “always” normally stay near the main verb in the new structure, and the overall time reference must remain the same.

Step-by-Step Solution:
Step 1: Identify the object in the active sentence. Here, “the questions of the students” is the object that receives the action. Step 2: Move this object to the subject position in the passive sentence: “The questions of the students ...”. Step 3: Keep the tense as simple present. The plural subject “questions” requires the auxiliary “are” in the passive: “are answered”. Step 4: Insert the adverb of frequency “always” near the auxiliary or main verb: “are always answered”. Step 5: Add the doer of the action with the preposition “by”: “by the tutor”. Step 6: Combine all elements to form the full passive sentence: “The questions of the students are always answered by the tutor.” Step 7: Compare this with the given options and select the one that matches exactly.

Verification / Alternative check:
To verify correctness, convert the passive sentence back into active voice. Starting from “The questions of the students are always answered by the tutor”, we move “the tutor” to the subject position, keep the tense as simple present, revert to the active form of the verb “answers”, and restore the object “the questions of the students”. This reconstruction yields the original sentence. This round-trip check confirms that option “The questions of the students are always answered by the tutor” is the accurate passive form.

Why Other Options Are Wrong:
Option A: Uses “is” with the plural noun “questions”, which violates subject–verb agreement. Option B: “Questions answered by the tutor are by the students” is logically incorrect because it wrongly suggests that questions belong to the students in a confusing way and lacks a clear verb for the main clause. Option D: Uses “is” again with a plural subject and has awkward structure that does not correspond to the active sentence. Option E: This remains in active voice with a fronted adverbial and does not provide a passive construction at all.

Common Pitfalls:
Students often forget to adjust the auxiliary “to be” according to the number of the new subject, leading to errors like “is” with plural nouns. Another common mistake is misplacing adverbs such as “always”, which sometimes changes emphasis or makes the sentence sound unnatural. It is also important to ensure that the agent phrase introduced by “by” correctly reflects the doer of the action and does not alter the meaning of the original sentence.

Final Answer:
The correct passive voice form of the sentence is The questions of the students are always answered by the tutor.