What is the result of a client request of the Source servlet with no query string？（）

• A、 The output “filterAdded = null” is written to the response stream.
• B、 The output “filterAdded = addedByFilter” is written to the response stream.
• C、 An exception is thrown at runtime within the service method of the Source servlet.
• D、 An exeption is thrown at runtime within the service method of the Destination servlet.