Explanation
Robocopy (Robust File Copy) is a command-line tool that can copy files and folders between Windows servers or computers. It has many features and options that can ensure all the data is copied consistently, such as retrying failed copies, resuming interrupted copies, copying permissions and attributes, mirroring source and destination directories, and logging the copy progress and results. Verified References: [Robocopy], [File copy]

The subnet mask is most likely containing an error that prevents the application server from communicating with the newly installed database server. The subnet mask is a binary number that defines how many bits of an IP address are used for the network portion and how many bits are used for the host portion. The subnet mask determines which devices belong to the same network or subnet and can communicate directly with each other without routing or switching devices. The subnet mask of the database server is 255.255.O.O, which means that all 32 bits of its IP address are used for the network portion and none for the host portion, which is invalid and makes it unreachable by any other device on any network or subnet. The subnet mask of the application server is 255.O.O.O, which means that only 8 bits of its IP address are used for the network portion and 24 bits are used for the host portion, which is also uncommon and makes it incompatible with most networks or subnets. References: [CompTIA Server+ Certification Exam Objectives], Domain 4.0: Networking, Objective 4.1: Given a scenario, configure network settings for servers.

The correct answer is D. per-core.
The per-core licensing model was created by software companies in response to the increasing density of processors. This model is used for software that runs on servers with multi-core processors, and the licensing fee is based on the number of cores. This way, the software vendors can charge more for software that runs on servers with more processing power1