What are two uses for External IDs? (Choose two.)

What would a developer do to update a picklist field on related Opportunity records when a modification to the associated Account record is detected?

A company wants to create an employee rating program that allows employees to rate each other. An employee's average rating must be displayed on the employee record. Employees must be able to create rating records, but are not allowed to create employee records. Which two actions should a developer take to accomplish this task? choose 2 answers

A developer must create an Apex class, contactcontroller, that a Lightning component can use to search for Contact records. User of the Lightning component should only be able to search Contact records to which they have access. Which two will restrict the records correctly?

A developer needs to join data received from an integration with an external system with parent records in Salesforce. The data set does not contain the Salesforce IDs of the parent records, but it does have a foreign key attribute that can be used to identify the parent.
Which action will allow the developer to relate records in the data model without knowing the Salesforce ID?
Create a custom field on the child object of type Foreign Key