The correct answers are A. Public Groups, D. Roles and Subordinates, and E. Users.

For a custom object with Private sharing, manual sharing is used to open access to selected records on a case-by-case basis. Salesforce manual sharing allows individual records to be shared with users, public groups, and roles. Salesforce Classic manual sharing also lets the user select the type of group, user, role, or territory to add.

B. Private Groups is not the standard Platform App Builder answer here.

C. Permission Set Groups is incorrect because permission set groups grant permissions, not manual record-level sharing.