Which of the following indicates the greatest solar flare intensity?

Solar flares are classified by their X-ray brightness in the wavelength range of 1 to 8 angstroms. The classification system uses the letters A, B, C, M, and X, with each letter representing a 10-fold increase in energy output. Among the choices provided, Class X represents the most intense solar flares. These extreme events can trigger planet-wide radio blackouts and long-lasting radiation storms. Class Z is an entirely fictitious distractor, and Class M is a moderate flare that is one step below Class X.