Step 1: Understanding the Question:
The question asks us to transform a given declarative or assertive sentence into its equivalent interrogative (question) form.
The original sentence is: ``He rarely speaks in English to his friends.''
Step 2: Key Concepts and Grammar Rules:
To transform a simple present tense assertive sentence with a singular third-person subject (``He'') into an interrogative sentence, we must use the auxiliary verb ``does''.
When the auxiliary verb ``does'' is introduced, the main verb must revert to its base form or bare infinitive (``speak'' instead of ``speaks'').
The adverb ``rarely'' is a semi-negative word and retains its position directly before the main verb.
Step 3: Detailed Explanation:
• Option (A): ``Is he rarely speaks...'' is grammatically incorrect because the auxiliary verb ``is'' cannot be paired with a simple present active verb like ``speaks'' in this manner.
• Option (B): ``Does he rarely speaks...'' is incorrect because it uses both the auxiliary ``does'' and the conjugated verb ``speaks''. This is a double-marking error.
• Option (C): ``Do he rarely speaks...'' is incorrect because the plural auxiliary ``do'' is used with the singular third-person pronoun ``he'', violating subject-verb agreement.
• Option (D): ``Does he rarely speak in English to his friend?'' is grammatically correct. It correctly matches the singular third-person subject ``he'' with the auxiliary ``does'' and uses the base form verb ``speak''.
Step 4: Final Answer:
Thus, Option (D) is the correct interrogative transformation.