The correct answer is option 2: wireless local area network (WLAN). Wi-Fi in a computer refers to the ability of the computer to connect to the internet or other devices without the need for physical wired connections. It allows the computer to connect to a network or router wirelessly using radio waves.

Option 1, wired local area network (LAN), refers to a network that uses physical Ethernet cables to connect devices. This is not the correct answer because Wi-Fi specifically refers to wireless connections.

Option 3, high fidelity, refers to the quality and accuracy of audio reproduction. This is not the correct answer as it is unrelated to Wi-Fi in a computer.

Option 4, high efficiency, is a vague statement that does not specifically relate to Wi-Fi in a computer. It is not the correct answer.

Therefore, the correct answer is option 2: wireless local area network (WLAN), as it accurately describes the ability of a computer to connect to the internet or other devices without physical wired connections, using radio waves.