When building the database layer of a Salesforce application using exclusively declarative development, the following options are relevant:
Option A: Roll-up summaries
Valid Declarative Tool.
Roll-up summary fields allow calculations (SUM, COUNT, MIN, MAX) on child records in a master-detail relationship.
They are created declaratively.
Custom objects and fields form the core of the database schema.
They are created using the Setup menu without code.
Relationships (lookup, master-detail, and many-to-many via junction objects) are established declaratively.
They define how objects relate to each other.
Flows are used for process automation and logic.
They are part of the application logic layer, not the database layer.
Option E: Triggers
Requires Code (Not Declarative).
Triggers are written in Apex code.
They are not part of declarative development.
Conclusion:
To build the database layer declaratively, the developer should use Roll-up summaries (A), Custom objects and fields (C), and Relationships (D).
Reference:
Roll-Up Summary Fields
Option C: Custom objects and fields
Valid Declarative Tool.
Creating Custom Objects and Fields
Option D: Relationships
Valid Declarative Tool.
Object Relationships Overview
Incorrect Options:
Option B: Flows
Not Part of the Database Layer.