Under identical conditions, for a single modulating frequency, FM and PM are indistinguishable. Now if the modulating frequency is reduced, then

• A. phase modulation index as well as frequency modulation index decrease
• B. phase modulation index as well as frequency modulation index increase
• C. phase modulation index will remain constant whereas frequency modulation index will increase
• D. phase modulation index will decrease whereas frequency modulation index will remain constant