**Rule:** The Future Perfect Continuous Tense (will have been + verb-ing) is used to emphasize the duration of an action ('for eight straight hours') leading up to a specific time in the future ('By 10 PM tonight'). It focuses on the continuous nature of the activity over that period.

**Rule:** This is a Zero Conditional sentence (if + simple present, ... simple present). It is used to state general truths or scientific facts where the result of the condition is always the same. The boiling of water at 100 degrees is a scientific fact. Option (a) would be used for a specific future result (First Conditional), but for a general truth, simple present is correct.

**Rule:** The Simple Present Tense is used to describe future events that are part of a fixed schedule, routine, or timetable. As this is a weekly meeting, it's a scheduled event. Option (a) is for flexible arrangements. Options (b) and (d) are less common for fixed, repeating schedules.

**Rule:** The negative form of the Future Perfect Tense (will not have + past participle) is used to state that an action will not be finished by a specific future deadline. The speaker predicts the projects will be incomplete at the time of the inspector's visit. Option (d) describes an action not in progress, which is a different meaning.

**Rule:** In a future time clause beginning with a conjunction like 'after', the Simple Present Tense is used to refer to the future event. The main clause uses the future tense ('I will have'). Therefore, 'ends' is the correct form. Using 'will' in the time clause is grammatically incorrect.

**Rule:** The Simple Future Tense ('will' + base verb) is used to express a spontaneous decision, offer, or promise made at the moment of speaking. The speaker is offering help on the spot. Option (b) 'am going to help' would imply a pre-existing plan to help. Option (a) 'am helping' (Present Continuous) would suggest the action is already in progress. Option (d) 'help' is the Simple Present.

**Rule:** The Present Continuous Tense ('is/are' + verb-ing) is used to talk about fixed personal arrangements in the near future. A birthday party is a classic example of a planned event. Option (a) would be a prediction, not a plan. Option (b) is simple present. Option (d) is future perfect.

**Rule:** Verbs of belief or expectation, like 'expect', 'think', 'believe', are typically followed by the Simple Future with 'will' to make a prediction. Option (d) is also grammatically possible, but 'will' is the most common and natural choice after 'I expect'. Options (a) and (b) are incorrect tenses.

**Rule:** The Simple Future with 'will' is used to make a spontaneous offer of help at the moment of speaking. The first sentence sets up the situation, and the second sentence is an immediate offer. Option (d) would imply a pre-existing intention to help, which is less fitting for a spontaneous offer. Options (a) and (c) are incorrect.

**Rule:** To ask about an action that will be in progress at a specific time in the future, the Future Continuous Tense (will be + verb-ing) is used. The question is about the activity at the exact time of 9 PM. Option (d) is also correct and very common for asking about plans. Option (b) asks what will be completed by that time. Option (c) is simple present, used for habits.