The uploaded study guide identifies B. Grid System as the correct SLDS resource for responsive design.

A responsive interface needs its layout to adapt as the available screen width changes. The Grid System is the resource selected by the guide because it provides the structural mechanism for arranging interface content into flexible rows and columns.

This directly addresses page-level responsiveness: content can be organized so that it uses available horizontal space appropriately and can be repositioned or wrapped as the viewport changes.

Option A, Design Tokens, addresses reusable design values. Tokens can support consistency for properties such as spacing, color, or other design attributes, but the question specifically asks what the designer should use for responsive layout design.

Option C, Component Blueprints, provides structural guidance for individual SLDS components rather than serving as the primary layout system for responsive page organization.

The key study-guide distinction is therefore between component styling/resources and layout architecture. When the issue is adapting page composition to different screen sizes, the Grid System provides the relevant SLDS mechanism.

This makes the grid an essential foundation for designing Salesforce interfaces that remain organized and usable across varying viewport dimensions.

Study Guide reference/topics: SLDS Grid System, responsive design, rows and columns, adaptive layouts, Salesforce Lightning Design System.

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