**Rule**: For a Past Perfect Tense sentence, the passive voice structure is **Object + had + been + V3 + by + Subject**. Adverbs like 'already' are typically placed between the auxiliary verb 'had' and 'been'. - **Correct Answer (c)**: The object 'him' becomes 'He'. The verb form 'had already been warned' correctly reflects the Past Perfect passive and the position of the adverb. - **Incorrect Answer (a)**: This incorrectly changes the tense to Simple Past. - **Incorrect Answer (b)**: This incorrectly changes the tense to Present Perfect. - **Incorrect Answer (d)**: While grammatically understandable, placing 'already' after 'been' is less standard and can be awkward.

**Rule**: When the active sentence uses 'has to' or 'have to', the passive form is **Object + has/have to + be + V3**. The subordinate clause ('before I leave') remains unchanged. - **Correct Answer (c)**: The object 'this task' becomes the subject. Since 'task' is singular, it takes 'has to be', followed by the past participle 'finished'. The rest of the sentence remains the same. - **Incorrect Answer (a)**: 'has been finished' is the passive of the Present Perfect Tense, not of 'have to'. - **Incorrect Answer (b)**: 'must' is a different modal, though similar in meaning. - **Incorrect Answer (d)**: 'was to be' incorrectly changes the tense and meaning to a past plan.

**Rule**: When the active sentence uses 'has to'/'have to', the passive form is **Object + has/have to + be + V3**. - **Correct Answer (c)**: The object 'this package' becomes the subject. Since 'package' is singular, it takes 'has to be', followed by the past participle 'sent'. - **Incorrect Answer (a)**: 'is to be' implies a plan, which is different from the obligation of 'have to'. - **Incorrect Answer (b)**: 'had to be' incorrectly changes the tense to the past. - **Incorrect Answer (d)**: 'has been sent' is the passive of the Present Perfect Tense, not of 'have to'.

**Rule**: When a reporting verb (like believe, think, consider) is followed by an object and a to-infinitive, the passive structure is **New Subject (object from active) + is/was + V3 (of reporting verb) + to-infinitive**. The agent 'by them' is often omitted. - **Correct Answer (a)**: The object 'him' becomes the subject 'He'. The verb 'believe' (Simple Present) becomes 'is believed'. The infinitive phrase 'to be innocent' remains unchanged. Omitting 'by them' is natural. - **Incorrect Answer (b)**: This incorrectly changes the tense to Simple Past. - **Incorrect Answer (c)**: This omits 'to be', which is grammatically incorrect in this structure. - **Incorrect Answer (d)**: This is another possible passive form ('It is believed...'), but option (a) is the most direct transformation of the given sentence structure.

**Rule**: For an interrogative sentence in the Simple Present Tense starting with 'What', the passive structure is **What + is/am/are + 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 'is meant' is the correct singular passive form for the Simple Present 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)**: The word order is incorrect and awkward.

**Rule**: For an interrogative sentence with 'will have to' and a phrasal verb starting with 'Who', the passive structure is **By whom + will + object + have to be + V3 + preposition?** - **Correct Answer (c)**: 'Who' becomes 'By whom'. The structure 'will...have to be paid for' is the correct passive form for the future necessity, retaining the preposition 'for'. The word order is correct for a question. - **Incorrect Answer (a)**: This omits 'have to', changing the meaning. - **Incorrect Answer (b)**: This is the passive of the Future Perfect Tense. - **Incorrect Answer (d)**: 'would' is an incorrect modal change.

**Rule**: For a sentence in the Past Continuous Tense, the passive voice structure is **Object + was/were + being + V3 + by + Subject**. - **Correct Answer (d)**: The object 'widespread damage' becomes the subject. Since 'damage' is uncountable, the singular verb 'was' is used, followed by 'being' and the past participle 'caused'. - **Incorrect Answer (a)**: This incorrectly changes the tense to Simple Past. - **Incorrect Answer (b)**: This incorrectly changes the tense to Present Perfect. - **Incorrect Answer (c)**: This incorrectly changes the tense to Present Continuous.

**Rule**: For a negative sentence in the Past Perfect Tense, the passive structure is **Object + had + not + been + V3 + by + Subject**. - **Correct Answer (c)**: The object 'the book' becomes the subject. The verb form 'had not been finished' is the correct passive construction for a negative sentence in the Past Perfect Tense. - **Incorrect Answer (a)**: This incorrectly changes the tense to Simple Past. - **Incorrect Answer (b)**: This incorrectly changes the tense to Present Perfect. - **Incorrect Answer (d)**: 'being' is incorrect; the past participle 'been' is required.

**Rule**: For a Simple Past Tense sentence with two objects (indirect 'me' and direct 'a job'), either can become the subject of the passive sentence. - **Correct Answer (d)**: Both (a) and (b) are correct passive transformations. - In (a), the direct object 'A job' becomes the subject. The passive verb is 'was offered', and the indirect object 'me' is preceded by 'to'. - In (b), the indirect object 'me' becomes the subject 'I'. The passive verb is 'was offered', and the direct object 'a job' follows. - **Incorrect Answer (a)**: This is correct, but (b) is also a valid transformation. - **Incorrect Answer (b)**: This is correct, but (a) is also a valid transformation. - **Incorrect Answer (c)**: This incorrectly changes the tense to Present Perfect.

**Rule**: For an interrogative sentence with the 'be going to' future form starting with 'Who', the passive structure is **By whom + is/am/are + object + going to be + V3?** - **Correct Answer (c)**: 'Who' changes to 'By whom'. The object 'this room' is singular, so 'is' is used, followed by the object and the correct passive structure 'going to be cleaned'. The word order is correct for a question. - **Incorrect Answer (a)**: This changes the structure to the 'will' future. - **Incorrect Answer (b)**: The word order is incorrect for an interrogative sentence. - **Incorrect Answer (d)**: 'who' is the incorrect case; 'whom' is required after the preposition 'By'.