Looking at the answer options:

Delay your departure until you are certain that the correct fuel was loaded --> CORRECT. Fuelling with Jet-A into a piston engined aircraft will cause engine damage or failure. Jet-A is not designed for piston engines and will have different ignition temperatures and give the potential for detonation.

Ensure you pay the invoice before departing --> INCORRECT. You need to confirm if Jet-A was loaded into your aircraft before starting the engine.

Ensure you conduct power checks at the appropriate RPM when using Jet-A fuel --> INCORRECT. You need to confirm if Jet-A was loaded into your aircraft before starting the engine.

Take a fuel sample in the normal way, this will show up any fuel contamination --> INCORRECT. The fuel sample is effective for checking for contamination such as water, not so much to verify the fuel type loaded.

Aviation Gasoline (AVGAS) is used by certain piston engine aircraft and is subject to stringent specifications set forth by the Directorate of Engine Research and Development (DERD). One such specification, DERD 2485, outlines the precise requirements for aviation gasoline. The octane rating of AVGAS is denoted by its grade; for instance, AVGAS 100 indicates a fuel with a 100 octane rating. High-performance engines with elevated compression ratios typically require higher octane fuels to operate efficiently and effectively.

Each grade of AVGAS is dyed a different colour to make it easier to identify: