What type of sample is taken from the fuel system of the aircraft to ensure quality?

The correct answer is a fuel sample. Taking a fuel sample from the aircraft's fuel system is a critical procedure to ensure the quality of the fuel being used. This practice helps in identifying any contaminants or impurities that could affect the performance and safety of the aircraft. The sample is typically examined for clarity, color, and the presence of water or other foreign substances.

By analyzing the fuel sample, maintenance personnel can ensure that the fuel meets the required specifications and is safe for use in the aircraft. This is particularly important, as any issues with the fuel can lead to operational failures or compromises in safety during flight operations.

While visual inspections, weight checks, and temperature readings are important aspects of aircraft maintenance, they do not specifically assess fuel quality in the way that taking a fuel sample does. Thus, focusing on taking a fuel sample is an essential step in maintaining the integrity and safety of the aircraft's operations.