**Rule:** The Future Perfect Continuous Tense (will have been + verb-ing) is used to highlight the duration ('for three weeks') of an ongoing action up to a specific point in the future ('By the end of this month'). It focuses on how long the activity will have continued. Option (a) doesn't emphasize the duration already passed.

**Rule:** The Future Perfect Tense (will have + past participle) is used to describe a state or action that will be completed or will have existed for a duration by a certain time in the future. 'For three days' specifies the duration of the state ('being without food') up to the future point 'By the time the rescue team arrives'. Therefore, 'will have been' is the correct form.

**Rule:** The phrase 'I'm afraid' is often followed by 'will' or 'won't' to politely state an inconvenient future fact or decision. 'Won't be able' is the standard and polite way to express future inability. Option (d) 'am not going to be' is possible, but 'won't be' is more common in this polite refusal context.

**Rule:** The Future Continuous Tense (will be + verb-ing) is used to describe a future action that will be in progress when another action happens. The action of 'talking' will be ongoing at the moment the phone call comes in. Option (b) suggests the talking will start at that moment, which is less likely.

**Rule:** The Future Perfect Passive voice (will have been + past participle) is used because the subject ('package') is receiving the action, and the action will be completed by a specific future time ('by this time tomorrow'). Option (a) is future continuous active. Option (b) is simple present active. Option (d) is simple present passive.

**Rule:** The Simple Future with 'will' is used for making predictions. Adverbs like 'probably', 'perhaps', or 'maybe' are often used with 'will' to show the degree of certainty. This is a general prediction about the weather. 'is going to rain' would be used if there were visible dark clouds (present evidence).

**Rule:** In reported speech, when a promise about the future is reported, 'will' is often retained to reflect the original promise. 'The politician promised, "Taxes will not increase."' Thus, 'will not increase' is the correct form. Option (c) 'would not increase' would be used if the reporting verb was in the past (e.g., 'He promised he would...').

**Rule:** The Future Continuous Tense (will be + verb-ing) can describe an action that will happen in the normal course of events in the future. It's a prediction of what will be happening at that moment. When the concert ends, the process of people leaving will be in progress. Option (b) 'will have poured' suggests the action will be complete, which is unlikely at the exact moment the concert ends. Options (c) and (d) are incorrect tenses.

**Rule:** The Future Perfect Tense (will have + past participle) is used to express that an action will be completed before another future event. The speaker predicts that the action of the best seats being taken ('gone') will be finished before they manage to get their tickets. Option (a) does not emphasize this completion.

**Rule:** The 'be going to' future is used to talk about intentions or plans. It is implied that the new CEO has an intention to make changes. It is a prediction of future events based on present knowledge. Option (b) is also possible for future plans. Option (a) is incorrect. Option (d) is present perfect.