The correct answer is C. Sketch Plugin. The study guide explicitly associates this tool with the requirement to rapidly create Salesforce-oriented designs and prototypes using SLDS resources such as components, tokens, and patterns.

The key phrase is “quickly mock up Salesforce User Interface experiences.” The designer needs a design-oriented resource rather than an implementation or validation mechanism. According to the guide, the Sketch Plugin provides the appropriate design workflow for working with reusable SLDS assets while creating prototypes.

Option A, the Lightning Design System Unmanaged Package, is not the design-tool solution keyed for this mockup requirement.

Option B, SLDS Validator, is oriented toward checking or validating implementation rather than providing the prebuilt design resources the UX Designer needs to compose a visual prototype.

The question reinforces the distinction between design tooling and development tooling. At the prototyping stage, the designer needs assets that can be quickly assembled into Salesforce-consistent screens without recreating base interface patterns from scratch.

Using a plugin built around SLDS resources also improves consistency between proposed designs and Salesforce visual conventions. Therefore, the study guide selects the Sketch Plugin as the tool best suited to rapid SLDS-based mockup creation.

Study Guide reference/topics: SLDS resources, Sketch Plugin, prototypes, prebuilt components, design patterns.

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