Which pair of words best completes the sentence: Lower level protocols guarantee higher level protocols will function without stating specifically how this will be accomplished?

Which pair of words best completes the sentence: Lower level protocols guarantee higher level protocols will function without stating specifically how this will be accomplished?

• A. Higher Lower
• B. Lower Higher
• C. Lower Lower
• D. Higher Higher

Answer: (B)

The sentence is testing layering and abstraction: lower-level components provide services to higher-level ones through a stable interface, hiding how those services are actually performed. The best pair to complete the sentence is the combination that keeps the relationship in the correct order—lower-level protocols supplying guarantees to higher-level protocols. Saying “Lower level protocols guarantee higher level protocols will function without stating specifically how this will be accomplished” captures the idea that higher layers can rely on the lower layers to offer necessary functionality without needing to know the inner workings. It reflects the contract between layers: lower layers handle details, expose a simple interface, and ensure higher layers can operate. The other options would alter who is guaranteeing whom or would create mismatches in how the levels relate, which doesn’t fit the intended dependency and abstraction.

The sentence is testing layering and abstraction: lower-level components provide services to higher-level ones through a stable interface, hiding how those services are actually performed. The best pair to complete the sentence is the combination that keeps the relationship in the correct order—lower-level protocols supplying guarantees to higher-level protocols. Saying “Lower level protocols guarantee higher level protocols will function without stating specifically how this will be accomplished” captures the idea that higher layers can rely on the lower layers to offer necessary functionality without needing to know the inner workings. It reflects the contract between layers: lower layers handle details, expose a simple interface, and ensure higher layers can operate. The other options would alter who is guaranteeing whom or would create mismatches in how the levels relate, which doesn’t fit the intended dependency and abstraction.