1. A, C
Skinny tables contain a subset of frequently used fields and improve query performance; custom indexes speed up filtering, while increasing heap size isn’t configurable and converting all relationships to master-detail is impractical.

2. C
Coexistence Style MDM keeps each system authoritative for its domain while maintaining a golden record, unlike Registry, Consolidation, or Transaction styles.

3. C
SOQL inside loops can exceed limits; SOQL must be moved outside the loop and bulkified.

4. B
OWD Private with Role Hierarchy allows managers visibility while restricting others.

5. B
Master-detail requires a parent, supports cascade delete, and enables roll-ups; lookup does not.

6. B
Big Objects store billions of infrequently accessed records cost-effectively with limited queries.

7. C
Roll-up summary fields aggregate child records, unlike formula fields.

8. C
Encrypted fields cannot be used in criteria-based sharing rules because they cannot be evaluated.

9. B
SOQL returns up to 50,000 records per transaction before hitting a limit exception.

10. B
Salesforce Connect gives real-time access to external data without storing it locally.

11. A, B
Apex managed sharing uses custom RowCause values and persists through ownership changes but cannot reduce access.

12. A
The formula triggers only when StageName changes to Closed Won and CloseDate is in the past.

13. A
Ownership skew occurs when one user owns over 10,000 records, causing performance and locking issues.

14. A
Serial approval with criteria supports conditional routing like sending to Finance only when amount > $5,000.

15. C
Implicit sharing grants Account read access to Opportunity owners, not Contact owners.

16. C
Batch Apex handles large data by processing chunks with fresh limits, unlike @future or Queueable.

17. A
Territory hierarchy works like role hierarchy, giving higher territories inherited access.

18. B
Field History Tracking logs old and new values for up to 20 fields for auditing.

19. A, C
Formula fields reference parent fields and are calculated in real time; they don’t store data or trigger workflows.

20. B
Bulk API with parallel processing is best for large imports, and disabling triggers prevents recursive limits.

21. C
Salesforce applies the most permissive access across sharing rules.

22. D
Lookup relationships can block parent deletion when child records exist; validation rules can’t run on delete.

23. B
FOR UPDATE locks records to prevent concurrent modifications and avoid race conditions.

24. C
Scoping Rules auto-filter records so external/API users only see relevant data.

25. C
External lookup relationships reference external data sources through Salesforce Connect.

26. C
Trigger.new contains all new field values (including lookup fields) during insert; Trigger.old isn’t available.

27. B
Permission Set Groups combine multiple Permission Sets for easier assignment.

28. B
Matching Rules define duplicate criteria, while Duplicate Jobs use them to find and merge duplicates.