E7E02:What is the function of a reactance modulator?

Direct answer summary (2024-2028 NCVEC pool)

The official correct answer for E7E02 is Produce PM or FM signals by varying a capacitance.

The key fact is Produce PM or FM signals by varying a capacitance. Match that fact to the exact condition in the question; the other choices describe a different rule, band, component, or operating situation.