**Rule**: For active sentences using the 'be going to' future form, the passive structure is **Object + is/am/are + going to be + V3**. - **Correct Answer (d)**: The object 'the guests' becomes the subject. The structure 'are going to be welcomed' is the correct passive conversion. - **Incorrect Answer (a)**: This is the passive of the Present Continuous tense. - **Incorrect Answer (b)**: This incorrectly changes the tense to the past. - **Incorrect Answer (c)**: This changes the structure to the 'will' future.

**Rule**: For sentences with modal verbs (like must), the passive structure is **Object + modal verb + not + be + V3**. The agent 'by us' is often omitted. - **Correct Answer (a)**: The object 'The rules' becomes the subject. The modal 'must not' is followed by 'be' and the past participle 'violated'. The agent 'by us' is correctly omitted for a general rule. - **Incorrect Answer (b)**: 'should' is a different modal, implying advice rather than a strong prohibition. - **Incorrect Answer (c)**: 'need not' suggests a lack of necessity, which changes the meaning. - **Incorrect Answer (d)**: 'must not have been' is the passive form for a past modal, which changes the tense.

**Rule**: For a sentence in the Past Perfect Tense, the passive voice structure is **Object + had + been + V3 + by + Subject**. - **Correct Answer (c)**: The object 'the village' becomes the subject. The verb form 'had been destroyed' is the correct passive construction for 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)**: This incorrectly changes the tense to Past Continuous.

**Rule**: For an interrogative Simple Past Tense sentence with two objects starting with 'Who', either object can become the subject in the passive form, which starts with **'By whom'**. - **Correct Answer (d)**: Both (b) and (c) are correct passive transformations. - In (c), the indirect object 'them' becomes the subject 'they', requiring the plural verb 'were'. - In (b), the direct object 'these manners' becomes the subject, also requiring the plural verb 'were', and the indirect object is expressed as 'to them'. - **Incorrect Answer (a)**: This incorrectly changes the tense to Present Perfect. - **Incorrect Answer (b)**: This is correct, but (c) is also valid. - **Incorrect Answer (c)**: This is correct, but (b) is also valid.

**Rule**: For an interrogative sentence in the Simple Past Tense starting with a 'Wh-' word, the passive structure is **Wh- word + was/were + object + V3 + by + subject?** - **Correct Answer (a)**: The 'Wh-' word 'Why' remains at the beginning. The object 'my advice' is singular, so 'was' is used, followed by the past participle 'ignored'. - **Incorrect Answer (b)**: This incorrectly changes the tense to Simple Present. - **Incorrect Answer (c)**: This is not in the correct interrogative word order; the auxiliary verb 'was' should come before the subject 'my advice'. - **Incorrect Answer (d)**: This incorrectly changes the tense to Present Perfect.

**Rule**: The verb 'surprised' in the passive voice is typically followed by the preposition **'at'** to indicate the cause. The active sentence is in the Simple Past Tense. - **Correct Answer (a)**: The object 'everyone' becomes the subject. The passive verb 'was surprised' is correct for the Simple Past. The preposition 'at' is idiomatically correct. - **Incorrect Answer (b)**: This incorrectly changes the tense to Present Perfect. - **Incorrect Answer (c)**: This incorrectly changes the tense to Simple Present. - **Incorrect Answer (d)**: While 'by' is sometimes used, 'at' is generally the preferred preposition with 'surprised' in this context.

**Rule**: For an interrogative sentence in the Future Simple Tense starting with 'Who', the passive structure is **By whom + will/shall + object + be + V3?** - **Correct Answer (c)**: 'Who' changes to 'By whom'. The modal 'will' is used, followed by the object 'the team', 'be', and the past participle 'led'. - **Incorrect Answer (a)**: 'would' is an incorrect modal change. - **Incorrect Answer (b)**: 'who' is the incorrect case; 'whom' is required after the preposition 'By'. - **Incorrect Answer (d)**: This word order is not standard for formal interrogative sentences.

**Rule**: For sentences with modal verbs (like can), the passive structure is **Object + modal verb + be + V3**. Adverbs are usually placed after the main verb. - **Correct Answer (c)**: The object 'This puzzle' becomes the subject. The modal 'can' is followed by 'be' and the past participle 'solved'. The adverb 'easily' is correctly placed after the verb. - **Incorrect Answer (a)**: 'could' is a different modal and changes the meaning from ability to possibility. - **Incorrect Answer (b)**: Placing the adverb between 'be' and the past participle ('be easily solved') is possible but less common than placing it after the verb phrase. - **Incorrect Answer (d)**: Placing the adverb between the modal and 'be' ('can easily be solved') is also a possible adverb position, but (c) is the most standard and clear construction.

**Rule**: For active sentences using the 'be going to' future form, the passive structure is **Object + is/am/are + going to be + V3**. - **Correct Answer (b)**: The object 'the plan' becomes the subject. The structure 'is going to be approved' is the correct passive conversion of 'is going to approve'. - **Incorrect Answer (a)**: This is the passive of the Present Continuous tense ('is approving'), not the 'going to' future. - **Incorrect Answer (c)**: This changes the structure to the 'will' future. - **Incorrect Answer (d)**: This introduces the idea of necessity ('has to'), which was not in the original sentence.

**Rule**: When the active sentence uses structures like 'is to', 'am to', 'are to', 'was to', or 'were to' to indicate a plan or arrangement, the passive form is **Object + is/am/are/was/were to + be + V3**. - **Correct Answer (a)**: The object 'my old car' becomes the subject. The structure 'was to be sold' is the correct passive form corresponding to the active 'was to sell'. - **Incorrect Answer (b)**: 'had to be' implies obligation, which is a different meaning. - **Incorrect Answer (c)**: 'was being sold' is the passive of the Past Continuous Tense. - **Incorrect Answer (d)**: 'has to be' incorrectly changes the tense and meaning to present obligation.