Client virtualization involves installing an application on a server and enabling multiple users to run the application simultaneously via virtualized sessions. This eliminates the need for individual installations on local machines.
Why Not B (Software as a Service): SaaS delivers software over the internet and does not require local installations but is managed by a third party, not the organization itself.
Why Not C (Sandboxing): Sandboxing is for isolating applications for security testing, not for concurrent user access.
Why Not D (Embedded software): Embedded software is installed on hardware devices, not shared across multiple users.
CompTIA A+ Exam Reference: Core 1 (220-1101), Section 4.2, virtualization concepts.

Client-side virtualization guest machines require isolation from other guest machines to maintain their security. Isolation ensures that each virtual machine is separated from others and runs its own operating system and applications, making it less vulnerable to attacks from other guest machines. References:
CompTIA A+ Certification Exam Objectives 220-1002 - Virtualization and cloud computing - 4.1

Switches only send data to the specific computer, while hubs send data to all computers inside the network.
References: CompTIA A+ Certification Exam Guide, Exam 220-1001, Page 323

Duplex printing allows printing on both sides of a paper, which can significantly reduce paper consumption and costs associated with buying paper. This makes duplex printing the best feature for cutting costs on consumables.
References:
* CompTIA A+ Core 1 Exam Objectives Section 3.6: Given a scenario, deploy and configure multifunction devices/printers and settings.