Which of the following is a valid Group D call sign format for Technician class?

Erklärung

Group D call signs have the 2x3 shape, a two-letter prefix, one numeral and a three-letter suffix, which is what KF1XXX is. KA1X is 2x1 and W1XX is 1x2; both belong to Group A and are issued only to Amateur Extra class licensees.