Port 21 is used by FTP (File Transfer Protocol) for file transfers. Port 53 is for DNS, port 68 is for DHCP, and port 389 is for LDAP. Understanding standard network ports is essential in CompTIA A+ Core 1 objectives, especially in networking and troubleshooting scenarios.

* Reasoning: A cable tester capable of testing Power over Ethernet (PoE) functionality can verify whether the switchport is providing the required power to the phone. This tool measures both the presence of data and the voltage or wattage being provided through the Ethernet cable.
* This is the most effective way to confirm that PoE is available on the port.
Why the Other Options Are Incorrect:
* A. Network tap:
* A network tap is primarily used to monitor network traffic, not to test for PoE availability. It cannot verify if power is being supplied through the Ethernet cable.
* C. Loopback plug:
* A loopback plug is used to test the functionality of a network port by creating a loop for transmitted and received signals. It does not measure or verify PoE availability.
* D. Toner probe:
* A toner probe is used for tracing and identifying network cables. It cannot test for PoE functionality.
Practical Example:
A PoE phone might not turn on due to a misconfigured or faulty switchport. Using a cable tester capable of measuring PoE would help the technician determine if the switchport is supplying sufficient power to the phone.
CompTIA A+ Exam Objective Alignment:
* Objective 2.1: Identify common networking hardware and tools, including PoE-enabled devices and cable testers.

The main reason to use a virtual machine as a sandbox is to test new software in a safe environment without risking the integrity of the host operating system. Using a virtual machine enables the testing of software and allows for the isolation of the software from the host system. References: CompTIA A+ Certification Study Guide, Tenth Edition, pg. 409

Using a USB 3.1 flash drive with BitLocker to Go installed is the best option for complying with corporate policy for data protection when copying files to portable media. References: CompTIA A+ Certification Exam Guide, Ninth Edition, Chapter 12

The most likely answer is C. The pen batteries need recharging.
An active touch pen is a stylus that uses a battery to power features such as pressure sensitivity, buttons, or Bluetooth connectivity. If the pen batteries are low or depleted, the pen may stop working or become inaccurate1. To fix this issue, you should recharge the pen batteries using the provided charger or cable, or replace them with new ones if they are not rechargeable1.
The other options are less likely to cause the issue. A scratched tablet screen may affect the touch sensitivity, but it should not affect the pen functionality. The pen software may need updating to improve performance or compatibility, but it should not stop the pen from working altogether. Software updates may disable the pen if they change the settings or drivers, but this can be fixed by re-enabling the pen or reinstalling the drivers2.
References:
1: Troubleshoot your Surface Pen - Microsoft Support
2: Windows 10 touch screen: active pen works, finger does not - Super User