**Rule:** The Future Perfect Tense (will have + past participle) is used for an action that will be completed before another moment in the future. 'By the end of their tour' is the future point by which the action of performing in 50 cities will be finished. Option (a) 'will be performing' suggests they will be in the middle of a performance at that time. Options (c) and (d) are present tenses and are incorrect.

**Rule:** Both the Present Continuous ('is departing') and the Simple Present ('departs') can be used for scheduled future events. Present continuous is very common for personal travel plans and arrangements. Option (a) is also correct but (b) is equally, if not more, common in spoken English for this context.

**Rule:** The Future Simple Passive ('will be' + past participle) is the standard way to talk about a formal, planned future event where the subject is the receiver of the action. The report cannot publish itself. Option (a) is active. Option (d) is also active. Option (c) is for regular schedules, but this is a one-time future event.

**Rule:** The Future Perfect Tense (will have + past participle) is used to express the completion of an action (or a number of actions) by a specific point in the future. 'By the time she is forty' is the future deadline by which she will have completed visiting many countries. Option (b) describes an ongoing action.

**Rule:** The Simple Future with 'will' is used to make general predictions about the distant future. This is a prediction about a long-term technological shift. Option (d) is also possible, but 'will' is very common for these kinds of general, long-range forecasts. Options (a) and (b) are incorrect.

**Rule:** The Simple Future with 'will' is used to state a future fact or a scheduled event that is not part of a personal plan. This is a statement about how the software is programmed to behave in the future. Option (b) would imply a personal arrangement. Option (a) is for fixed timetables. Option (d) is present perfect.

**Rule:** The question asks about the duration of an action up to a specific point in the future, which requires the Future Perfect Continuous Tense (will have been + verb-ing). 'By the time you move to London' sets the future point. Option (a) 'will you be studying' (Future Continuous) asks if the action will be in progress at that time, not about its duration. Options (b) and (d) are present tenses.

**Rule:** The Simple Future with 'will' is used for making promises. The speaker is promising to call in the future. The time clause 'as soon as I have any news' correctly uses the simple present. Option (d) is for prior plans, but this sounds more like a promise made now.

**Rule:** When asking about future events that are part of a fixed schedule or timetable, it is common to use the Simple Present Tense. The structure is 'What time does [subject] start?'. Option (c) 'is...starting' is also very common and correct for asking about future arrangements. Option (b) is future continuous. Option (d) is future perfect.

**Rule:** Both Simple Present ('leaves') and Present Continuous ('is leaving') can be used for future events that are part of a fixed schedule or timetable. The simple present is very common for transport schedules. Present continuous is also correct as it refers to a fixed personal arrangement. However, for official timetables, simple present is the most standard choice.