The correct answer is: A. 1.25 MHz.
GSM (Global System for Mobile Communications) is a second-generation (2G) digital cellular network technology. It was developed in Europe in the 1980s and 1990s, and is now the most widely used mobile phone standard in the world.
GSM uses a frequency-division multiple access (FDMA) system, which means that each user is assigned a separate frequency channel. The carrier separation in GSM is 1.25 MHz, which means that there are 124 channels available in each band.
The other options are incorrect because they are not the carrier separation used in GSM. Option B, 200 kHz, is the carrier separation used in the 1G Advanced Mobile Phone System (AMPS) standard. Option C, 30 kHz, is the carrier separation used in the 1G Nordic Mobile Telephone (NMT) standard. Option D, 300 kHz, is the carrier separation used in the 1G Total Access Communication System (TACS) standard.
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