Diagnosing topology — in a series–parallel circuit, components that are in parallel share the same voltage. Therefore, observing that voltages are not shared identifies components that are NOT in parallel. Is this diagnostic statement valid?

Introduction / Context:
When troubleshooting mixed series–parallel networks, it helps to know which measurements reveal series versus parallel groupings. Parallel elements share the same node pair; consequently, they must have the same voltage across them at a given instant. This item tests whether “non-shared voltages” imply “not parallel.”

Given Data / Assumptions:

• Lumped linear circuit; DC or instantaneous AC measurement.
• Accurate voltage measurements across candidate components.
• No significant wiring drops skewing readings between supposed common nodes.

Concept / Approach:
Parallel definition: components connected across the same two nodes. Voltage is a difference in electric potential between two points. If two components are parallel, the voltage difference across each is identical. Conversely, if two components exhibit different voltages, they cannot share exactly the same two nodes, so they are not in parallel (though they might still be part of a broader parallel path plus series segments).

Step-by-Step Solution:

Verification / Alternative check:
Use a schematic or continuity tester to verify that the terminals of both components connect to the same nodes. Voltage equality is a necessary condition for parallel; coupled with node tracing, it becomes sufficient for diagnosis.

Why Other Options Are Wrong:

• Incorrect: It would imply parallel elements need not share voltage, which contradicts the definition.
• Valid only for AC / only for equal resistors: Parallel voltage sharing is topology-driven, independent of frequency and resistor equality.

Common Pitfalls:
Measuring with floating references or swapping meter leads; interpreting small measurement differences due to probe placement or wiring resistance as proof against parallelism without verifying nodes.

Final Answer:
Correct — if voltages are not shared, the elements are not in parallel.