**Rule**: For interrogative sentences in the Simple Past Tense starting with 'What', the passive structure is **What + was/were + V3 + by + subject?**

- **Correct Answer (a)**: The 'Wh-' word 'What' remains at the beginning and acts as the subject of the passive sentence. The verb 'was eaten' is the correct singular passive form for the Simple Past Tense.
- **Incorrect Answer (b)**: This incorrectly changes the tense to Simple Present.
- **Incorrect Answer (c)**: This incorrectly changes the tense to Present Perfect.
- **Incorrect Answer (d)**: This incorrectly changes the tense to Past Continuous.

**Rule**: For sentences with a reporting verb (like say, believe, think) and a 'that'-clause, a common passive form starts with **'It'**. The structure is **It + is/was + V3 (of reporting verb) + that-clause**. Since the reporting verb 'say' is in the present tense, the passive uses 'is said'. The universal truth in the clause remains unchanged.

- **Correct Answer (b)**: The sentence is correctly transformed by starting with 'It', followed by the passive form 'is said', and the original 'that'-clause.
- **Incorrect Answer (a)**: The word order is awkward and changes the tense of the reporting verb to past.
- **Incorrect Answer (c)**: This incorrectly changes the tense of the reporting verb to Present Perfect.
- **Incorrect Answer (d)**: This structure alters the original sentence significantly and changes the tense.

**Rule**: To change a Present Perfect Tense sentence to passive voice, we use **Object + has/have + been + V3**. When the subject is an indefinite pronoun like 'someone', it is often omitted in the passive voice.

- **Correct Answer (c)**: The object 'My wallet' becomes the subject. 'has been stolen' is the correct passive verb form for the present perfect tense. The agent 'by someone' is correctly omitted as it is understood.
- **Incorrect Answer (a)**: This incorrectly changes the tense to Simple Past.
- **Incorrect Answer (b)**: This incorrectly changes the tense to Simple Present.
- **Incorrect Answer (d)**: This incorrectly changes the tense to Past Perfect.

**Rule**: For interrogative sentences starting with 'Who' in the Simple Past Tense, the passive form begins with **'By whom'**, followed by the helping verb, the object (which becomes the subject), and the past participle of the main verb. The structure is **By whom + was/were + object + V3?**

- **Correct Answer (a)**: 'Who' changes to 'By whom'. The object 'this beautiful piece of music' is singular, so the helping verb 'was' is used. The past participle of 'compose' is 'composed'.
- **Incorrect Answer (b)**: 'Who' is the nominative case and is incorrect here. The objective case 'whom' should be used after the preposition 'by'.
- **Incorrect Answer (c)**: This option incorrectly changes the tense to Simple Present by using 'is'. The original sentence is in the Simple Past Tense.
- **Incorrect Answer (d)**: This is not a passive construction; it's an active voice sentence in the Present Perfect Tense.

**Rule**: A sentence in the Future Simple Tense is converted to passive voice using the structure: **Object + will/shall + be + V3 + by + Subject**.

- **Correct Answer (b)**: The object 'him' becomes the subject 'He'. The verb form 'will be pardoned' is the correct passive construction for the future simple tense.
- **Incorrect Answer (a)**: 'would' is an incorrect change of the modal verb.
- **Incorrect Answer (c)**: This incorrectly changes the tense to Simple Present.
- **Incorrect Answer (d)**: This incorrectly changes the tense to Present Perfect.

**Rule**: When the active sentence has a gerund (verb + -ing) as the object, the passive form uses **being + V3** (past participle).

- **Correct Answer (a)**: The gerund phrase 'my father taking me' becomes the passive gerund phrase 'being taken'. The rest of the sentence remains the same.
- **Incorrect Answer (b)**: The reflexive pronoun 'myself' is unnecessary and makes the sentence awkward.
- **Incorrect Answer (c)**: This changes the grammatical structure from a gerund phrase to a subordinate clause, altering the sentence's style.
- **Incorrect Answer (d)**: 'Took' is the simple past form of the verb, not the past participle 'taken', which is required here.

**Rule**: For a sentence in the Simple Past Tense, the passive voice structure is **Object + was/were + V3 + by + Subject**.

- **Correct Answer (d)**: The object 'the whole building' becomes the subject. Since it is singular, 'was' is used, followed by the past participle 'destroyed'.
- **Incorrect Answer (a)**: This incorrectly changes the tense to Simple Present.
- **Incorrect Answer (b)**: This incorrectly changes the tense to Present Perfect.
- **Incorrect Answer (c)**: This incorrectly changes the tense to Past Continuous.

**Rule**: For sentences with modal verbs (like must, can, should), the passive structure is **Object + modal verb + be + V3**. The agent 'by you' is often omitted when it is clear or implied.

- **Correct Answer (a)**: The object 'The answers' becomes the subject. The modal 'must' is followed by 'be' and the past participle 'written'. The agent 'by you' is correctly omitted.
- **Incorrect Answer (b)**: Using 'should' changes the modal from one of strong obligation to one of advice. Including 'by you' is not necessary.
- **Incorrect Answer (c)**: 'must have been' is the passive form for a past modal, which changes the tense and meaning.
- **Incorrect Answer (d)**: This is an awkward and unnatural construction.

**Rule**: When verbs of perception (like see, hear, watch) are followed by a bare infinitive (verb without 'to') in the active voice, the passive form uses a **'to'-infinitive**. The structure is **Object + was/were + V3 + to-infinitive**.

- **Correct Answer (b)**: The object 'them' becomes the subject 'They'. The verb 'were seen' is the correct passive form for the Simple Past. The bare infinitive 'go' changes to the 'to'-infinitive 'to go'.
- **Incorrect Answer (a)**: This is incorrect because the bare infinitive 'go' must be changed to a 'to'-infinitive in the passive voice.
- **Incorrect Answer (c)**: This incorrectly changes the tense to Past Perfect.
- **Incorrect Answer (d)**: Using the present participle 'going' is possible but changes the meaning slightly, implying the action was in progress. The direct conversion of the bare infinitive is the 'to'-infinitive.

**Rule**: For a negative sentence in the Past Perfect Tense, the passive voice structure is **Object + had + not + been + V3 + by + Subject**.

- **Correct Answer (a)**: The object 'Their homework' becomes the subject. The verb form 'had not been done' is the correct passive construction for a negative sentence in the Past Perfect Tense.
- **Incorrect Answer (b)**: This incorrectly changes the tense to Simple Past.
- **Incorrect Answer (c)**: This incorrectly changes the tense to Present Perfect.
- **Incorrect Answer (d)**: This incorrectly changes the tense to Simple Present.