What is the primary use of a Junction Object?

Correct answer: To implement a many-to-many relationship

Option C is correct because a Junction Object in Salesforce is a custom object with two master-detail relationships pointing to two different parent objects, which is the standard pattern for modeling a many-to-many relationship between those parents. Option A is incorrect because Junction Objects have no impact on query performance; optimizing queries is done through indexes, skinny tables, and selective SOQL filters. Option B is incorrect because data encryption in Salesforce is handled by Shield Platform Encryption or Classic Encryption at the field level, not by Junction Objects. Option D is incorrect because restricting field visibility is accomplished through field-level security settings or permission sets, not through the structure of a Junction Object.