**Rule**: For a Present Continuous Tense sentence, the passive structure is **Object + is/am/are + being + V3 + by + Subject**.

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

**Rule**: Imperative sentences that make a request (often starting with 'Please' or 'Kindly') are converted into passive voice using the phrase **'You are requested to'** followed by the base form of the verb.

- **Correct Answer (d)**: The word 'Please' indicates a polite request. Therefore, 'You are requested to...' is the most appropriate passive structure.
- **Incorrect Answer (a)**: The 'Let' structure is more common for commands than for polite requests.
- **Incorrect Answer (b)**: 'Should' suggests advice or obligation, which is different from a request.
- **Incorrect Answer (c)**: 'ordered' is incorrect as the original sentence is a request, not a command.

**Rule**: For a Present Continuous Tense sentence with a phrasal verb, the passive structure is **Object + is/am/are + being + V3 + preposition/adverb + by + Subject**.

- **Correct Answer (c)**: The object 'the old theatre' becomes the subject. The verb form 'is being pulled down' correctly reflects the passive voice of the Present Continuous Tense, keeping the particle 'down' with the verb. The agent 'by them' is omitted.
- **Incorrect Answer (a)**: This incorrectly changes the tense to Simple Present.
- **Incorrect Answer (b)**: This incorrectly changes the tense to Past Continuous.
- **Incorrect Answer (d)**: This incorrectly changes the tense to Present Perfect.

**Rule**: An imperative sentence starting with 'Let us' which indicates a suggestion is best converted to passive voice using the structure: **'It is suggested that...'**

- **Correct Answer (b)**: This option correctly captures the suggestive tone of the original sentence. 'Let us' is interpreted as a proposal.
- **Incorrect Answer (a)**: This changes the imperative mood to a simple future statement.
- **Incorrect Answer (c)**: While the 'Let' structure is used for commands, it is less common for suggestions starting with 'Let us'. The form in (b) is more appropriate.
- **Incorrect Answer (d)**: 'is to be' implies a plan or an order, which does not fit the suggestive nature of the sentence.

**Rule**: When the active sentence uses 'will have to', the passive form is **Object + will have to + be + V3**.

- **Correct Answer (d)**: The object 'my trip' becomes the subject. The structure 'will have to be cancelled' is the correct passive form for the future necessity.
- **Incorrect Answer (a)**: This is the passive of the Future Perfect Tense.
- **Incorrect Answer (b)**: 'would' is an incorrect modal change.
- **Incorrect Answer (c)**: This omits 'have to', changing the meaning.

**Rule**: When the active sentence uses 'will have to', the passive form is **Object + will have to + be + V3**.

- **Correct Answer (c)**: The object 'this assignment' becomes the subject. The structure 'will have to be completed' is the correct passive form for the future necessity.
- **Incorrect Answer (a)**: This is the passive of the Future Perfect Tense.
- **Incorrect Answer (b)**: 'would' is an incorrect modal change.
- **Incorrect Answer (d)**: 'is to be' incorrectly changes the tense and meaning to a present plan.

**Rule**: For sentences with past modals (modal + have + V3), the passive structure is **Object + modal + have been + V3 + by + Subject**.

- **Correct Answer (d)**: The object 'me' becomes 'I'. The past modal passive form 'should have been informed' is the correct construction.
- **Incorrect Answer (a)**: 'should be informed' is the passive form for a present modal ('should inform'), not a past modal.
- **Incorrect Answer (b)**: While 'ought to' is similar to 'should', it is a different modal and not a direct conversion.
- **Incorrect Answer (c)**: 'must' changes the meaning from advice about a past action to a strong deduction.

**Rule**: Negative imperative sentences expressing a command or strong advice are often converted to passive voice using the structure: **Let + object + not + be + V3**.

- **Correct Answer (b)**: This option correctly applies the 'Let' structure for a negative command. 'the weak' is the object, followed by 'not be' and the past participle 'insulted'.
- **Incorrect Answer (a)**: While 'warned' is a possibility, the 'Let' structure is a more direct and standard passive conversion.
- **Incorrect Answer (c)**: This structure implies a rule, which is a slightly different nuance.
- **Incorrect Answer (d)**: This treats the command as advice, which is also a valid interpretation, but (b) is a more direct conversion of the imperative form.

**Rule**: For a negative sentence in the Simple Past Tense with two objects, the indirect object can become the subject. The passive structure is **Object + was/were + not + V3**.

- **Correct Answer (d)**: The indirect object 'us' becomes the subject 'We'. The passive verb form 'were not given' correctly reflects the negative Simple Past tense. The direct object 'any homework' follows.
- **Incorrect Answer (a)**: This incorrectly changes the tense to Past Continuous.
- **Incorrect Answer (b)**: This incorrectly changes the tense to Simple Present.
- **Incorrect Answer (c)**: While grammatically possible, making the indirect object the subject (as in d) is often more natural.

**Rule**: When the active sentence uses 'has to'/'have to', the passive form is **Object + has/have to + be + V3**.

- **Correct Answer (d)**: The object 'its expenses' becomes the subject. Since 'expenses' is plural, it takes 'have to be', followed by the past participle 'reduced'.
- **Incorrect Answer (a)**: 'have been reduced' is the passive of the Present Perfect Tense.
- **Incorrect Answer (b)**: 'are to be' implies a plan, not necessity.
- **Incorrect Answer (c)**: 'had to be' incorrectly changes the tense to the past.