Final answer:
Phones that use an Electronic Serial Number (ESN) to identify them are mostly CDMA phones. (Option B)
Step-by-step explanation:
CDMA phones use an Electronic Serial Number (ESN) for identification. Unlike GSM phones which utilize SIM cards, CDMA devices are linked to network carriers and use ESNs for verification. However, newer technologies like LTE and 5G are moving away from ESNs to IMEI numbers. CDMA stands for Code Division Multiple Access, which is a digital cellular technology that uses spread spectrum techniques. Unlike GSM phones that use a SIM card to identify and verify subscribers, CDMA phones are directly linked to a specific network, and the ESN is used to validate the device's identity with the carrier. Examples of carriers that have used CDMA technology in the past include Verizon and Sprint in the United States.
It's important to note that with the advent of LTE and 5G technologies, the significance of ESN is diminishing as carriers move towards newer identification methods such as the IMEI (International Mobile Equipment Identity).