Step 1: Understanding the Concept:
This question requires converting a 'Wh-' question from direct to indirect speech.
Step 2: Key Rules for Conversion:
1. Reporting Verb: 'said to' changes to 'asked'.
2. Conjunction: The 'Wh-' word ('Why') itself acts as the conjunction. 'that' is not used.
3. Sentence Structure: The question form (verb before subject: 'are you') changes to a statement form (subject before verb: 'he was'). The question mark is removed.
4. Tense Change: The present continuous tense ('are working') changes to the past continuous tense ('was working').
5. Pronoun Change: 'you' (referring to 'him') changes to 'he'.
Step 3: Detailed Explanation:
Applying the rules to 'I said to him, "Why are you working so hard ?"':
- 'I said to him' becomes 'I asked him'.
- 'Why' remains as the conjunction.
- 'are you working' becomes 'he was working'. The tense changes from present continuous to past continuous, and the pronoun 'you' becomes 'he'.
- The structure becomes a statement: 'why he was working so hard'.
Combining these gives: I asked him why he was working so hard.
Let's check the options:
(A) 'why he was working so hard' - Correctly uses the statement structure and tense change.
(B) 'why was he working so hard' - Incorrectly retains the question structure (verb before subject).
(C) & (D) 'why had he been working...' - Incorrect tense change. Present continuous becomes past continuous, not past perfect continuous.
Step 4: Final Answer:
The correct indirect speech is I asked him why he was working so hard.