Which type of field should an app builder create?

Cloud Kicks wants to start tracking how many shoe subscriptions have been sold for each shoe catalog. A master-detail relationship exists between the Subscription__c and the Shoe__c objects.

Which type of field should an app builder create?
A . Roll-up summary field
B . Lookup field
C . Master-detail relationship field
D . Number field

Answer: A

Explanation:

To start tracking how many shoe subscriptions have been sold for each shoe catalog, a roll-up summary field should be created. A roll-up summary field calculates values from related records on a master-detail relationship. It can count, sum, min, or max numeric values from child records on a parent record.