Which two operations can be performed using a formula field? Choose 2 answers

A developer must modify the following code snippet to prevent the number of SOQL queries issued from exceeding the platform governor limit. public class without sharing OpportunityService( public static List<OpportunityLineItem> getOpportunityProducts(Set<Id> opportunityIds){ List<OpportunitylineItem> oppLineItems = new List<OpportunityLineItem>(); for(Id thisOppId : opportunityIds){ oppLineItems.addAll([Select Id FROM OpportunityLineItems WHERE OpportunityId = :thisOppId)]; } return oppLineItems; } } The above method might be called during a trigger execution via a Lightning component. Which technique should be implemented to avoid reaching the governor limit?

What is the value of the Trigger.old context variable in a Before Insert trigger?

Application Events follow the traditional publish-subscribe model. Which method is used to fire an event?

Which feature allows a developer to create test records for use in test classes?