**Rule**: For a sentence in the Past Continuous Tense, the passive voice structure is **Object + was/were + being + V3**. The agent 'by them' can be omitted. - **Correct Answer (c)**: The object 'the injured person' becomes the subject. Since it's singular, 'was' is used, followed by 'being' and the past participle 'carried'. The agent 'by them' is correctly omitted. - **Incorrect Answer (a)**: This incorrectly changes the tense to Simple Past. - **Incorrect Answer (b)**: This incorrectly changes the tense to Present Continuous. - **Incorrect Answer (d)**: This incorrectly changes the tense to Present Perfect.

**Rule**: For sentences using the modal-like structure 'will have to', the passive form is **Object + will have to + be + V3**. - **Correct Answer (d)**: The object 'new traffic rules' becomes the subject. The structure 'will have to be introduced' is the correct passive form for the future necessity. - **Incorrect Answer (a)**: This omits 'have to', changing the meaning from necessity to a simple future action. - **Incorrect Answer (b)**: This is the passive form of the Future Perfect tense, which is incorrect. - **Incorrect Answer (c)**: 'would' is an incorrect modal change and alters the meaning.

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

**Rule**: For a sentence in the Past Continuous Tense, the passive voice structure is **Object + was/were + being + V3 + by + Subject**. - **Correct Answer (c)**: The object 'an important issue' becomes the subject. Since it's singular, 'was' is used, followed by 'being' and the past participle 'discussed'. - **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 Present Continuous.

**Rule**: When the active sentence uses 'had to' with a phrasal verb, the passive form is **Object + had to + be + V3 + particle**. - **Correct Answer (d)**: The object 'the meeting' becomes the subject. The structure 'had to be called off' is the correct passive form for the past necessity, keeping the particle 'off' with the verb. - **Incorrect Answer (a)**: 'was to be' implies a past plan, which is a different meaning. - **Incorrect Answer (b)**: 'has to be' incorrectly changes the tense to the present. - **Incorrect Answer (c)**: 'had been called off' is the passive of the Past Perfect Tense.

**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 'the football match' becomes the subject. Since it's singular, 'was' is used, followed by 'being' and the past participle 'watched'. - **Incorrect Answer (a)**: This incorrectly changes the tense to Simple Past. - **Incorrect Answer (b)**: This incorrectly changes the tense to Present Continuous. - **Incorrect Answer (c)**: This incorrectly changes the tense to Past Perfect.

**Rule**: For a negative sentence in the Present Perfect Tense, the passive structure is **Object + has/have + not + been + V3 + by + Subject**. - **Correct Answer (b)**: The object 'the parcel' becomes the subject. The passive verb form 'has not been delivered' correctly reflects the negative Present Perfect tense. - **Incorrect Answer (a)**: This incorrectly changes the tense to Simple Past. - **Incorrect Answer (c)**: This incorrectly changes the tense to Past Perfect. - **Incorrect Answer (d)**: This incorrectly changes the tense to Simple Present.

**Rule**: When the active sentence uses a modal-like structure such as 'will have to', the passive form is **Object + will have to + be + V3**. - **Correct Answer (d)**: The object 'more staff' becomes the subject. The structure 'will have to be hired' is the correct passive form for the future necessity. - **Incorrect Answer (a)**: This omits 'have to', changing the meaning from future necessity to a simple future action. - **Incorrect Answer (b)**: 'would' is an incorrect modal change. - **Incorrect Answer (c)**: This is the passive form of the Future Perfect tense ('will have hired'), not 'will have to hire'.

**Rule**: A sentence in the Simple Past Tense is converted to passive voice using the structure: **Object + was/were + V3 + by + Subject**. The preposition 'by' is standard with the verb 'offend' to indicate the agent. - **Correct Answer (a)**: The object 'me' becomes the subject 'I'. The verb form 'was offended' is correct for the Simple Past Tense, and 'by' correctly introduces the agent. - **Incorrect Answer (b)**: This incorrectly changes the tense to Simple Present and uses the wrong preposition 'with'. - **Incorrect Answer (c)**: This incorrectly changes the tense to Present Perfect. - **Incorrect Answer (d)**: While 'at' can be used with some emotional verbs, 'by' is the standard choice for 'offended'.

**Rule**: When an intransitive verb phrase needs to be made passive, it often requires restructuring. Here, 'practice harder' can be nominalized to 'Harder practice'. - **Correct Answer (a)**: The phrase is restructured. 'Harder practice' becomes the subject, and the verb 'do' is introduced to carry the passive voice ('will have to be done'). This is the most natural-sounding conversion. - **Incorrect Answer (b)**: This is grammatically incorrect. - **Incorrect Answer (c)**: 'Harder' is an adverb and cannot be the subject. - **Incorrect Answer (d)**: While grammatically possible, it's more awkward than option (a).