**Rule:** The Simple Future with 'will' is used for a spontaneous decision made at the moment of speaking. The feeling of exhaustion leads to the immediate decision to take a break. Option (c) would imply a prior plan to take a break, which is less likely than a spontaneous reaction to feeling tired.

**Rule:** The 'be going to' form is used for predictions when there is present evidence for the future event. The 'dark clouds' are clear evidence that rain is imminent. Option (a) 'will rain' is used for predictions without present evidence or for spontaneous decisions. Option (c) 'rains' is Simple Present. Option (d) 'will have rained' (Future Perfect) is incorrect as it refers to a completed action in the future.

**Rule:** The Future Perfect Continuous Tense (will have been + verb-ing) is used to emphasize the duration of an action up to a specific point in the future. The duration is 'for twenty-five years', and the future point is 'Next month'. This tense perfectly captures the long service.

**Rule:** The Present Continuous Tense ('is/are' + verb-ing) is frequently used to talk about personal arrangements and fixed plans for the near future. The speaker has a pre-arranged plan to visit their grandparents. Option (b) would suggest a spontaneous decision, which is less likely in this context. Options (c) and (d) are incorrect.

**Rule:** The Future Simple Passive ('will be' + past participle) is needed because the 'law' is the object of the action 'to pass'. This structure is used for formal announcements and predictions about future events where the focus is on the action, not the agent. Option (a) is active. Option (b) is future perfect active. Option (d) is simple present active.

**Rule:** The Present Continuous ('is/are' + verb-ing) is very commonly used for fixed events in the near future, especially in informal contexts like this. 'is starting' emphasizes the immediacy of the scheduled event. Option (a) 'starts' is also correct for schedules. Option (d) is also possible to show a prediction based on the current time.

**Rule:** The future passive with 'be going to' ('is going to be' + past participle) is used to talk about planned future actions where the subject is the receiver of the action. 'The local council has plans' confirms this is a pre-decided action. Option (a) is also passive but 'going to' is strongly linked to existing plans.

**Rule:** The Future Perfect Continuous Tense (will have been + verb-ing) is used to express the duration of an action up to a certain point in the future. The duration is 'for twenty years' and the future point is 'by the time he retires'. Option (c) doesn't emphasize the duration. Options (b) and (d) are incorrect.

**Rule:** The Future Perfect Continuous Tense (will have been + verb-ing) is used to emphasize the duration ('for six months') of an action up to a point of completion in the future ('by the time it is finished'). It connects the duration of the work to its end point. Option (d) does not carry the same emphasis on the completed duration.

**Rule:** The Future Perfect Tense (will have + past participle) is used for an action that will be completed before another future action. 'Before you come home' is the second future action, setting the deadline for the completion of the painting. Option (d) 'will be painting' means the painting will be in progress when you come home. Options (a) and (c) are incorrect tenses.