Have some trouble.

The text says:

Frequency Bands and Channels

GSM has been allocated an operational frequency from 890 MHz to 960 MHz. To reduce possible interference, the MS and the BS use different frequency ranges (MS employ 890 MHz to 915 MHz and BS operate in 935 MHz to 960 MHz). GSM follows FDMA and allows up to 114 MSs to be serviced at the same time (frequency band of 25 MHz is divided into 124 Frequency Division Multiplexing (FDM) channels, each of 200 kHz s shown in the figure below).

I narrow the answer down to FDMA and TDMA. Can you explain the answer and why.

The 3 kHz analog voice signal is modulated onto 30 kHz channels.

Fequency Band used o Frequency band for the MS Frequency band for the BS 890 MHz 915 MHz 935 MHz 960 MHz Uplink (reverse Downlink (forward) 124 200 kHz 200 kHz 124 available FDM channels