B, D
Ramki and test are right, except for one detail included in https://developer.salesforce.com/docs/atlas.en-us.draes.meta/draes/draes_object_relationships_implicit_sharing.htm , which makes that the right answers are B and D:

Implicit sharing in Account ... "Not granted by the View All permission on the child object" 😉

A C should be the answer, if an user has access to case, contact or opportunity they will have read only access to the parent account

https://developer.salesforce.com/docs/atlas.en-us.draes.meta/draes/draes_object_relationships_implicit_sharing.htm

B D
Probably not to ALL (if case is not owned by a Account, then there is no access to such the Account)

A. Service reps will be able to access all UC contact records if they are controlled by parent: In Salesforce, when Contact records are set to "Controlled by Parent," their visibility is determined by the parent Account's visibility. If service reps have "View All" permissions on the Case object and if the Cases are related to Accounts, the reps will implicitly gain read access to the Accounts (due to case association) and thus to the Contacts associated with those Accounts. This setup ensures that service reps have access to necessary contact information while attending to customer requests.

C. Service reps will be able to access all the UC Account records due to Implicit Sharing: Implicit Sharing means that when users have access to a child record (like a Case associated with an Account), they may gain access to the parent record (the Account) as needed to perform their duties. In this context, "View All" on Cases doesn't directly grant access to all Account records universally; however, service reps would have access to Accounts related to the Cases they can view, enabling them to see relevant Account information when working on a Case. This access is crucial for providing comprehensive customer service, as it ensures reps have all the context needed to resolve Cases effectively....