What is the minimum total usable fuel required in the aircraft?

The minimum total usable fuel required in an aircraft is often determined by regulatory requirements to ensure safe operations under various conditions, including takeoff, landing, and during contingencies such as fuel diversion or holding patterns. The selected answer of 201 liters aligns with the regulatory guidelines pertaining to fuel minima for specific categories of flights, ensuring that the pilot has sufficient fuel reserves for safe operations.

In practice, 201 liters is likely calculated based on factors such as the aircraft's fuel consumption rate, flight duration, and any allowances for variations in weather conditions or unforeseen circumstances. Ensuring that an aircraft has at least this amount of usable fuel is crucial for safety, helping to prevent scenarios where a pilot might have to divert or turn back due to insufficient fuel.

The other options, while they all represent quantities of usable fuel, do not meet the specific regulatory requirements that would dictate a minimum of 201 liters. Hence, they fall short of the necessary fuel reserve that a pilot must maintain to ensure safety during a flight.