easyMultiple Choice
200-901 Practice Question: Which design principle suggests that a module…
Which design principle suggests that a module should be responsible for a single part of the functionality?
⚠ Common exam trap
Cisco often tests the distinction between Separation of Concerns and DRY, as candidates may confuse 'not repeating code' with 'assigning single responsibility' — the trap is that DRY is about code reuse, not module focus.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Separation of Concerns
Separation of Concerns (SoC) is the design principle that dictates each module or component should focus on a single, well-defined part of the functionality. In software development, this reduces coupling and increases cohesion, making code easier to maintain, test, and refactor. For example, in a Python Flask web application, separating route handling, business logic, and database access into distinct modules follows SoC.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Separation of Concerns
Why this is correct
Separation of Concerns assigns each module one distinct responsibility, directly satisfying the stem's requirement for a single part of the functionality. Unlike cohesion, which measures how strongly related a module's internals are, this principle prescribes the boundary itself, keeping unrelated functionality isolated so changes in one area do not ripple across others.
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YAGNI (You Aren't Gonna Need It)
Why it's wrong here
YAGNI advises against building features before they are needed; it says nothing about how responsibilities are divided within a module. The single-responsibility principle is the design rule that assigns one part of the functionality to each module, and YAGNI applies to deferring speculative features instead.
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DRY (Don't Repeat Yourself)
Why it's wrong here
DRY targets duplicated logic, not module scope; it advocates consolidating repeated code into one authoritative place. The stem asks about assigning one responsibility per module, which is the Single Responsibility Principle. DRY would be correct when the same validation routine is copy-pasted across several modules and should be extracted.
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KISS (Keep It Simple, Stupid)
Why it's wrong here
KISS advocates avoiding unnecessary complexity in a solution, not limiting a module to one responsibility. The stem describes cohesion of purpose, which is the Single Responsibility Principle. KISS would be the right principle when a working script is over-engineered with needless abstraction layers.
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