The Activity Timeline in Salesforce provides a chronological view of all past and upcoming interactions with a contact. This includes logged calls, emails, meetings, and tasks. It is a central feature to track engagement and manage customer relationships effectively.
* B. Details Tab: Displays static information about the contact, such as name, email, and address, but not interaction history.
* C. Contact History: Refers to changes made to a contact's field values over time, not interaction logs.
References from Salesforce Documentation:
* Activity Timeline Overview
* Working with Contacts

Salesforce operates on a multi-tenant architecture, where a single instance of the platform serves multiple customers (tenants). Each tenant's data is securely isolated, but they share common resources, such as server space, database instances, and updates. This approach ensures cost efficiency and scalability.
* A. Costs more than single-tenant architecture: Multi-tenancy reduces costs due to shared resources.
* B. Reserves resources per tenant: Resources are shared rather than reserved individually.
References from Salesforce Documentation:
* Salesforce Multi-Tenant Architecture Overview
* Multi-Tenant vs. Single-Tenant

Using the global search box is the best way to search the account records for the desired business using the fewest clicks. The global search box is a feature that allows the user to search for records across multiple objects and fields using keywords or phrases. The global search box also supports wildcards, operators, and filters to refine the search results. For example, the user could enter "Get*" in the global search box to find all account records that start with "Get". Using a list view of all accounts would not work, because a list view is a filtered set of records that display data in a tabular format. A list view does not support wildcards or operators, and it requires more clicks to apply filters and sort the records. Using a report of all accounts would not work, because a report is a tool that displays data from one or more objects in a tabular or graphical format. A report does not support wildcards or operators, and it requires more clicks to create, run, and filter the report.

Contacts to multiple accounts is a feature that allows a contact to be related to more than one account. This is useful for scenarios where a contact works at multiple companies or has different roles at different accounts.
Creating two contact records would result in duplicate data and confusion. Merging the two account records would not solve the problem of relating the contact to two accounts.