Consider an FM signal f(t) = cos [2πfct + β1 sin 2πf1t + β2 sin 2πf2t]. The maximum deviation of the instantaneous frequency from the carrier frequency fc is

• A. β1f1 + β2f2
• B. β1f2 + β2f1
• C. β1 + β2
• D. f1 + f2