Explanation
The set of APIs recommended to meet the requirements are Bulk API, Streaming API, Apex REST API, and Analytics REST API. Bulk API is a RESTful API that allows you to quickly load large amounts of data into Salesforce. Bulk API is suitable for the initial load of millions of records into the new org. Streaming API is a type of streaming event that notifies subscribers of changes to Salesforce records that match a SOQL query.
Streaming API is suitable for sending notifications of new and updated Accounts and Contacts to external systems. Apex REST API is an API that allows you to expose custom business logic as RESTful web services that can be accessed by external applications. Apex REST API is suitable for exposing custom business logic in a highly secure manner. Analytics REST API is an API that allows you to access analytics features, such as dashboards, lenses, datasets, and dataflows. Analytics REST API is suitable for scheduling nightly automated dataflows, recipes and data syncs. The other sets of APIs are not suitable for meeting all the requirements.
Chatter REST API is an API that allows you to access Chatter feeds and social data such as users, groups, followers, and files. Chatter REST API is not relevant for this scenario. Apex SOAP API is an API that allows you to expose custom business logic as SOAP web services that can be accessed by external applications.
Apex SOAP API is less preferable than Apex REST API because it requires more bandwidth and processing time due to the XML format. Tooling API is an API that allows you to build custom development tools or apps for Salesforce applications. Tooling API is not relevant for this scenario.