The Contact Delete process in Marketing Cloud removes contact data from the contact model but does not remove records from the data extensions themselves.
* Contact Delete Process: When you perform a Contact Delete in Contact Builder, it removes the contact data from the contact model but leaves the actual rows in the data extensions intact.
Salesforce Contact Deletion Process

To transform the date and time 'Data_Enrolled' from Daylight Savings time and fall back one hour, the developer should use the following AMPscript function:
%%=DateAdd(Data_Enrolled, -1, 'H')=%%
This function subtracts one hour from the 'Data_Enrolled' date and time.
References:
Salesforce Marketing Cloud AMPscript Date Functions
Salesforce Marketing Cloud Documentation

Regarding the Marketing Cloud SOAP API, the following statements are true:
* Most SOAP calls can be synchronous or asynchronous (B) - This means that API calls can either wait for the operation to complete (synchronous) or proceed with other tasks while waiting for the response (asynchronous).
* Uses XML in request and response body (C) - The SOAP API utilizes XML for both requests and responses, providing a standardized format for data interchange.
References:
Salesforce Marketing Cloud SOAP API Overview
Salesforce SOAP API Developer Guide

The Output function in AMPscript is used to include the result of interpreted code within a code block in the rendered content. This function ensures that the evaluated result of the code is included directly where the Output function is called.
* Example:
ampscript
Copy code
%%[ SET @message = "Hello, World!" ]%% %%=Output(@message)=%%
Salesforce AMPscript Output Function

A "401 Unauthorized" error typically indicates an issue with authentication or permissions. Since the Client ID and Client Secret have been successfully used in other REST calls, the most likely cause is insufficient permissions for sending emails.
* Check Send Permissions: Ensure that the appropriate permissions for sending emails have been granted to the Client ID and Client Secret in the Installed Packages. Without these permissions, the API call will fail with a 401 error.
Salesforce Installed Packages and Permissions