Final answer:
Cabin service should be suspended during descent and takeoff when passengers and crew are required to be seated with seatbelts fastened for safety reasons. Service may also be paused during turbulence or when the seatbelt sign is illuminated.
Step-by-step explanation:
The question asks about the appropriate times for cabin service suspension on a flight. Cabin service should be suspended during periods when it could pose a risk to the safety of the passengers and crew, or when the crew needs to be seated for safety reasons.
In the options provided, the correct answer is: b) During descent. During descent, the flight crew prepares for landing, which includes ensuring that the cabin is secure. This is a critical phase of flight where passenger movement should be limited, and the crew needs to be seated with seat belts fastened. It would not be safe to conduct cabin service at this time.
Option d) During takeoff is also a critical phase where cabin service must be suspended for the same safety-related reasons. While not listed in the options, cabin service is also paused during turbulence or whenever the seatbelt sign is on.
During boarding (option a), passengers are still settling in, so cabin service generally does not occur. During cruising (option c), cabin service is usually ongoing, as this is the safest and most stable phase of flight where passengers can comfortably eat and drink.