What should a pilot monitor during a flight to ensure safety?

Monitoring the fuel gauge and engine temperature is critical for ensuring the safety of a flight. The fuel gauge provides essential information about the amount of fuel remaining, which directly affects the aircraft's ability to complete the flight safely. A pilot must ensure that there is enough fuel to reach the destination, as well as reserve fuel for unexpected circumstances, such as diversions or extended holding patterns.

Engine temperature is also vital because it indicates the health and performance of the aircraft's engines. Overheating can lead to engine failure, which poses a significant safety risk during flight. By keeping an eye on these parameters, pilots can make informed decisions regarding the operation of the aircraft and respond proactively to any abnormalities that may arise, thereby enhancing safety for everyone on board.

The other choices focus on aspects that, while important, do not take precedence over the critical operational metrics like fuel and engine performance needed for maintaining flight safety. Monitoring passenger comfort and cabin pressure, for example, is important for overall comfort but does not directly influence the immediate safety of the aircraft in the same manner as fuel and engine temperature.