The correct answer is A. Mobile device management.

Mobile device management, or MDM, is the best solution for managing BYOD devices and protecting company data if a device is lost or stolen. MDM can enforce security policies such as screen locks, device encryption, remote wipe, containerization, application control, device compliance checks, and location tracking.

This is especially important in a BYOD environment because employees own the devices, but the organization still needs to protect corporate data stored or accessed on those devices.

Why the other options are incorrect:

B. Endpoint detection and response

EDR is used to detect, investigate, and respond to endpoint threats such as malware, suspicious behavior, and compromise. It is not the best tool for managing lost or stolen mobile devices.

C. Host-based intrusion detection system

A HIDS monitors activity on a host to detect suspicious behavior. It does not provide the mobile management features needed for BYOD risk reduction.

D. Data loss prevention

DLP helps prevent sensitive data from being leaked or transferred inappropriately, but MDM is the better answer for lost or stolen BYOD devices because it can enforce mobile security controls and perform remote wipe.

Therefore, the best tool is mobile device management.