On which object can an administrator create a roll-up summary field?

A developer is creating an enhancement to an application that will allow people to be related to their employer.
Which data model provides the simplest solution to meet the requirements?

Universal Containers has created a unique process for tracking container repairs. A custom field, status__c, has been created within the container__c custom object. A developer is tasked with sending notifications to multiple external systems every time the value of the status__picklist changes.
Which two tools should the developer use to meet the business requirement and ensure low maintenance of the solution?
Choose 2 answers

What can be used to override the Account's standard Edit button for Lightning Experience7

Account acct = {SELECT Id from Account limit 1}; Given the code above, how can a developer get the type of object from acct?