Answer: Must is high modality: it sounds certain, forceful and demanding. Might wish to reconsider is low modality: it sounds tentative and polite. Writers raise modality to sound confident and urgent, and lower it to sound reasonable and open.

Answer: Short, blunt sentences, as in "We cannot wait another year. Every month of delay costs lives. Act now.", create pace and urgency. Long sentences with qualifications, as in the measured extract, slow the reader down and suggest careful thought.

Answer: Understatement deliberately presents something as less serious than it is, which creates irony and invites the reader to share the writer's view. Example: describing a flooded school hall as "a little damp".

Model answer: Urgent: The northern bus service is failing the people who depend on it. Buses run late or not at all, and no one is told why. Students miss exams; workers lose shifts. The transport department must fix this timetable now. Wry: Residents of the northern suburbs have discovered a thrilling new game: guessing whether today's bus will arrive. Some days it is merely late; on others, it vanishes altogether, without the courtesy of a farewell. Perhaps the transport department could be persuaded to look at the timetable, if it can find a bus to bring it there.

Model answer: There is a particular sound that a group of teenagers makes when a teacher announces a group assignment. It is not quite a groan; it is more of a collective exhale, the sound of thirty people quietly calculating who will end up doing all the work. I have made that sound myself, many times, and I suspect most adults reading this have too. Schools love group work, and to be fair, they have their reasons. Employers say they want people who can collaborate. Research suggests that explaining an idea to a peer is one of the best ways to learn it. These are not small things. But somewhere between the research paper and the classroom, something has been lost. Too often a group assignment is not a lesson in collaboration but a lesson in endurance, in which the most anxious student does the most work and everyone receives the same mark. I am not arguing that group work should disappear. I am arguing that it should be designed as carefully as any other lesson. Tone: I chose a wry but measured tone, using gentle comedy in the opening, a concession to the other side and low-key modality so the reader trusts that my argument is fair.