To safely upgrade the Microsoft Windows 10 OS, it is essential to backup critical data (C) and ensure that you have the necessary device drivers (D). Backing up critical data protects against potential data loss during the upgrade process. Having the correct device drivers ensures that the hardware components function properly with the new OS version, preventing issues like loss of functionality or compatibility problems.

BitLocker is a full-disk encryption feature included with Windows Vista and later. It is designed to protect data by providing encryption for entire volumes. By encrypting the hard drive, BitLocker prevents unauthorized access to the data stored on the drive, securing it in case the laptop is lost or stolen. BitLocker is preferable over options like Windows Backup (which is for data recovery, not encryption), Shadow Copy (used for backup and does not encrypt data), and Trusted Platform Module (TPM, which is a hardware component used alongside BitLocker for securing encryption keys).

The correct answer is B. Swapping the cables for the monitors. When the second monitor is connected with the HDMI port, it is necessary to swap the cables for the monitors so that the mouse can move from the original monitor to the new monitor. This is because the HDMI port is designed to only support one monitor, and the mouse will not be able to move from one to the other without the cables being swapped.
According to CompTIA A+ Core 2 documents, "When connecting multiple displays to a system, the cables used to connect the displays must be swapped between the displays. For example, if a monitor is connected to a system using a VGA cable, the VGA cable must be moved to the next display to allow the mouse to move between the two displays."