When using purely declarative development to build the business logic layer in Salesforce, the following options are available:
Option A: Validation Rules
Reference:
"Validation rules verify that the data a user enters in a record meets the standards you specify before the user can save the record."
- Salesforce Help: Validation Rules
Option C: Record-Triggered Flow
"Record-triggered flows can be configured to run before or after the record is saved, making them a powerful declarative tool for business logic."
- Salesforce Help: Record-Triggered Flow
Why Other Options Are Incorrect:
Option B: Remote Actions require Apex code (annotated with @RemoteAction) and are used for making Apex methods callable from JavaScript, which is not declarative.
Option D: Batch Jobs are written in Apex and are used for processing large volumes of records asynchronously, which is programmatic development.