To solve this question, the user needs to have knowledge about the Debug class and its methods.
The Debug class is a class in C# that provides a set of methods, properties, and events to assist in debugging applications. It is mainly used for debugging purposes, such as tracing, logging, and error handling.
Now, let's go through each option and explain why it is right or wrong:
A. Assert( ): This is a method of the Debug class, which is used to check whether a condition is true or false. If the condition is false, it will stop the execution of the program and display an error message. Therefore, option A is not the correct answer.
B. Open(): This method is not a part of the Debug class. It is a method of the File class, which is used to open a file in the specified mode. Therefore, option B is the correct answer.
C. Flush( ): This is a method of the Debug class, which is used to clear the output buffer and send any pending messages to the listeners. Therefore, option C is not the correct answer.
The Answer is: B