Schema Builder is a tool that allows app builders to view and modify the data model of their Salesforce org. Some of the capabilities of Schema Builder are:
Creating and editing custom objects and fields
Creating and editing relationships between objects
Showing selected objects on a page
Editing custom settings
Schema Builder cannot be used to create a new record type or view page layouts in a new window.

The solution that an app builder should use to meet this requirement is master-detail relationship. A master-detail relationship is a type of relationship that creates a parent-child relationship between two objects, where the child records inherit the sharing and security settings of their parent record. The app builder can create a master-detail relationship between Supplier__c and SupplierItem__c objects, where Supplier__c is the parent object and SupplierItem__c is the child object. This way, when a Supplier__c record is deleted, all related SupplierItem__c records are also deleted automatically. Option A is incorrect because many-to-many relationship is not suitable for this requirement, as many-to-many relationship allows two objects to be linked in both directions through a junction object, but does not support cascading delete. Option B is incorrect because indirect lookup relationship is not suitable for this requirement, as indirect lookup relationship allows an external object to link with another object using an external ID field, but does not support cascading delete. Option C is incorrect because hierarchical relationship is not suitable for this requirement, as hierarchical relationship allows users to use a lookup field that links an object with itself, but does not support cascading delete.

Updating the account search layouts search results columns displayed and updating the account search filter fields can improve an end user's search experience by showing more relevant information and allowing more refined filtering. The view filter settings and the accounts tab columns displayed are not related to the search functionality

To have automatic posts on a record whenever a travel request has been approved, feed tracking should be used. Feed tracking enables field updates to be displayed in the Chatter feed of a record or a user profile. Users can follow records or users to see updates in their own feed. Feed tracking can be enabled for standard or custom objects and selected fields.

To insert a list of 25,000 records using deduplication for the Race_Track__c custom object, an app builder should use Data Loader. Data Loader is a tool that allows users to insert, update, delete, or export large amounts of data in Salesforce. Data Loader can also perform deduplication by matching records based on external ID fields or Salesforce record IDs. [Source]