In frequency modulation (FM), the amplitude of the carrier is kept constant but the frequency $f_c$ of the carrier is varied by the modulating signal.

The carrier frequency changes according to the strength of the modulating signal and value of modulation index ($m_f$) can be more than 1.

Therefore the correct match is as follows:

$\begin{array} \text {a.}\text{ Amplitude} & \text{2. Constant with Modulation} \\ \text {b. Carrier Frequency} & \text{1. Changes with Modulation} \\ \text {c. Value of Modulation Index} & \text {3. Can be greater than 1}\\ \end{array}$