To answer this question, we need to understand how an Integration Server service is invoked via an HTML form post.
When invoking an Integration Server service via an HTML form post, the form data is typically sent as key-value pairs in the request body. The key represents the name of the input parameter, and the value represents the data associated with that parameter.
In this case, the question states that a string named "xml" is being sent in the form data. When the Integration Server service is invoked, this string will appear in the pipeline as a string called "xml".
Option A) As a string called xml - This option is correct. The string named "xml" will appear in the pipeline as a string called "xml".
Option B) As an object called xml - This option is incorrect. The string will not be automatically converted into an object called "xml".
Option C) As a string called node - This option is incorrect. The question specifies that the string is named "xml", not "node".
Option D) As an object called node - This option is incorrect. The question specifies that the string is named "xml", not "node".
Therefore, the correct answer is A) As a string called xml.