A. Query Synchronized Data Extensions using a query activity to a Salesforce Data Extension, then send via Email Studio Send Flow
B. Import Salesforce Report through an import activity to a Salesforce Data Extension, then send to data extension using Email Studio email send
C. Assign the one million contacts from the report to a Salesforce campaign, and use a Single Step journey with Salesforce Campaign as an entry event
D. Send to a Salesforce Report from Marketing Cloud using Email Studio Send Flow
Explanation:
A synchronized data extension is a data extension that is automatically populated with data from Sales Cloud objects using Marketing Cloud Connect. A query activity is an automation studio activity that allows querying data from data extensions or data views using SQL statements. A Salesforce data extension is a type of data extension that stores data imported from Sales Cloud reports or campaigns using Marketing Cloud Connect. By querying synchronized data extensions using a query activity to a Salesforce data extension, the customer can segment contacts based on complex criteria without relying on Sales Cloud reports or campaigns. Then, by sending via Email Studio Send Flow to the Salesforce data extension, the customer can leverage tracking and reporting features of Marketing Cloud Connect.
References:
https://help.salesforce.com/articleView?id=sf.mc_co_data_integration_synchronized_data_sources.htm&type=5
https://help.salesforce.com/articleView?id=sf.mc_es_send_email_send_flow.htm&type=5