Types of operating system (distributed, embedded, multitasking, multiuser, real-time) and software development methodologies (waterfall, agile, extreme programming, spiral, rapid application development), with their merits and appropriate uses.

Levels-of-response question; reward a developed comparison reaching a justified judgement.

Waterfall runs sequential phases (analysis, design, implementation, testing, maintenance) with each completed before the next begins. It gives clear documentation and milestones and suits projects with stable, well-understood requirements, but it copes poorly with change because returning to an earlier phase is costly, and the product is only seen near the end.

Agile works in short iterations, delivering working increments and welcoming changing requirements through continuous customer feedback. This matches a startup whose requirements will evolve from user feedback, because each iteration can adjust direction. Its drawbacks are lighter documentation and a need for close, ongoing user involvement.

Conclusion: agile is the better fit here because the requirements are expected to change and early-user feedback is central; waterfall would lock in requirements too early. Top marks need the changing-requirements point linked explicitly to the agile iteration cycle.

Situation (2 marks): a safety-critical control system such as an aircraft fly-by-wire system, a car's anti-lock braking, a pacemaker or an industrial robot, where a response must occur within a strict deadline.

Key property (2 marks): a real-time OS must guarantee that processing completes within a fixed, predictable time (a deadline), because a late result is as useless or dangerous as a wrong one. It therefore uses deterministic scheduling that prioritises meeting deadlines over throughput. Markers reward a genuine deadline-driven scenario plus the guarantee of a bounded, predictable response time.