**Rule:** The Future Perfect Tense (will have + past participle) is used to indicate that an action will be completed by a specific future time. 'In five years' time' sets the future deadline by which the action of starting a business is expected to be finished. Options (d) is also plausible, suggesting the business will be in operation, but (a) focuses on the completion of the initial act of starting.

**Rule:** The Future Perfect Tense (will have + past participle) is used to talk about a change or action that will be completed by a specific future time. 'By 2050' is the deadline by which the transition to renewable energy as the main source will be complete. Option (c) is a simple prediction, but (d) emphasizes the completed state.

**Rule:** The Simple Future with 'will' is used to make a promise or a spontaneous decision at the moment of speaking. The speaker is promising to return the call. This is an on-the-spot decision in response to the current situation. Option (d) would imply a pre-existing plan to call back.

**Rule:** This is a First Conditional sentence expressing a future plan that is conditional on another event. 'is going to have' is used to show a pre-existing intention or plan. 'will have' would also be correct to state the resulting action, but 'is going to have' strongly implies it's a plan she has already made. Option (d) is for hypothetical situations.

**Rule:** The Future Perfect Tense (will have + past participle) is used to express that one future action will be completed before another future action starts. The action of arriving will be finished before the action of cooking is finished. Option (a) suggests the arrival will be in progress at that time.

**Rule:** The Future Perfect Passive voice (will have been + past participle) is required. The 'policy' is the object of the action. The action of announcing will be completed by a specific future deadline ('By this time tomorrow'). Option (a) is active. Option (b) is future continuous active. Option (c) is simple present active.

**Rule:** 'Shall' is used with 'I' and 'we' in questions to make a suggestion. 'Shall we leave now?' is a common way to suggest a course of action to a group. Option (a) would be a question about a prediction. Options (b) and (d) are grammatically incorrect.

**Rule:** The Future Continuous Tense (will be + verb-ing) is used to describe an action that will be in progress at a specific time in the future. 'This time tomorrow' pinpoints the exact moment when the action of taking the exam will be happening. Option (a) implies the exam will be finished by that time.

**Rule:** The Future Perfect Tense (will have + past participle) is used for an action that will be completed before another future event. The redecoration will be finished by the time the person returns. Option (d) 'will be redecorating' implies the action will be in progress upon return. Options (b) and (c) are incorrect tenses for this context.

**Rule:** This is a First Conditional sentence ('if' + simple present, ... 'will' + base verb) expressing a very likely future consequence of inaction. The main clause correctly uses 'will miss' to state the future result. Option (d) is for hypothetical situations. Options (a) and (c) are incorrect.