A quick action on the Account object can be used to create Opportunity records related to an Account. The quick action can pre-populate some fields based on the Account record, and also allow the user to input some fields. This would improve the process of creating Opportunity records

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: https://help.salesforce.com/articleView?id=relationships_considerations.htm&type=5 Roll-Up Summary Fields: https://help.salesforce.com/articleView?id=fields_about_roll_up_summary_fields.htm&type=5