A technician is troubleshooting Wi-Fi connection issues on a customer's laptop.

The next thing that the technician should investigate is D. Radio frequency.

Radio frequency is the range of electromagnetic waves that are used to transmit wireless signals. Different devices and networks use different radio frequencies, such as 2.4 GHz or 5 GHz, to communicate with each other. If there are multiple devices or networks using the same or overlapping radio frequencies, they can interfere with each other and cause Wi-Fi connection issues, such as intermittent disconnections, slow speeds, or poor quality .

To fix this issue, the technician can try changing the radio frequency or channel of the router or the laptop, to avoid interference from other sources. The technician can also use a tool such as Wi-Fi Analyzer to scan the nearby wireless networks and find the best frequency or channel to use. Alternatively, the technician can move the router or the laptop to a different location, away from potential sources of interference, such as cordless phones, microwaves, Bluetooth devices, or other routers .

The other options are less likely to be the reason for the issue. Firewall settings are software configurations that control the network traffic and security of a device. They may block some websites or applications from accessing the internet, but they should not affect the Wi-Fi connection itself. MAC address filter is a feature that allows the router to restrict access to specific devices based on their MAC addresses, which are unique identifiers for network interfaces. If the MAC address filter is enabled and the laptop’s MAC address is not on the allowed list, it will not be able to connect to the Wi-Fi network at all, not intermittently. Number of connected devices is the amount of devices that are using the same Wi-Fi network at the same time. This may affect the network performance or bandwidth, but it should not cause intermittent disconnections, unless the network is overloaded or unstable.