正解:D
A load balancer is a network device or service that distributes incoming network traffic across multiple servers, based on various criteria, such as availability, capacity, performance, or location. A load balancer can ensure that the servers' resources will be utilized efficiently, as well as improve reliability, scalability, and security. A load balancer can be hardware-based or software-based, or a combination of both. Reference:
https://www.comptia.org/training/books/a-core-1-220-1101-study-guide (page 79)