Salesforce Platform-App-Builder Online Access

To track the total number of trails associated with a park without writing code, the correct actions to take are:

Use a roll-up summary field on the Park record to show the total number of Trails (B). Roll-up summary fields calculate and display a value in a master record based on the values of fields in a detail record. They are used to count, sum, average, or get the minimum/maximum of values in related detail records.

Use a master-detail relationship between the Park and Trail objects (C). Master-detail relationships are necessary for roll-up summary fields as they allow the master object to control certain behaviors of the detail object and summarize data from those detail records.

A formula field (A) cannot dynamically count related records unless those records are linked via a master-detail relationship, and it cannot alone handle counts across related records without such a relationship. A lookup relationship (D) does not support roll-up summaries unless combined with additional tools like triggers or third-party apps, which involve coding or extra configuration outside standard object setup.

For more details, refer to the Salesforce Help documentation on master-detail relationships and roll-up summary fields:

Master-Detail Relationship: &type=5

Roll-Up Summary Fields: &type=5

 NOT(ISBLANK(Job_Accepted__c)) && ISCHANGED(Hire_Date__c) is the validation formula that the app builder should use to meet the requirement of preventing changes to Hire Date after Job Accepted is entered. This formula will return TRUE if Job Accepted is not blank and Hire Date is changed, which will display an error message and prevent saving the record. The other formulas are not correct or valid.

Workflow rule and an outbound message or Process Builder and Apex Code are two ways to integrate Salesforce with an external web service. Workflow rule can define criteria and actions for triggering an outbound message, which is an XML message sent to a designated endpoint URL. Process Builder can invoke Apex Code, which is a programming language that can make callouts to external web services using HTTP requests. Flow Builder and an outbound message or Process Builder and an outbound message are not possible combinations.