Comprehensive and Detailed Explanation (paraphrased, aligned to N10-009):

A proxy server (specifically a caching HTTP/HTTPS proxy) stores frequently accessed web objects and serves them locally to clients, reducing external bandwidth consumption and improving response times.

B. Load balancer distributes traffic across servers but does not inherently cache internet content.

C. Open relay is a misconfigured mail server that permits unauthorized relaying—this is a security issue, not a caching solution.

D. Code repository (e.g., for source control) isn’t related to web content caching.

References (CompTIA Network+ N10-009):

Domain: Network Standards, Protocols, and Implementations — Application-layer services (HTTP/HTTPS), proxies and caching behavior, performance optimization.

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