Any output manipulator function you create _____

The correct answer is: A. should take as an argument an instance of ostream as a reference.

An output manipulator function is a function that takes an instance of ostream as a reference and modifies the output stream in some way. For example, the endl manipulator function outputs a newline character to the output stream.

The other options are incorrect because:

• Option B is incorrect because an output manipulator function does not have to return void. For example, the setw manipulator function returns an instance of ostream.
• Option C is incorrect because an output manipulator function does not have to be a member function of the ostream class. For example, the endl manipulator function is not a member function of the ostream class.
• Option D is incorrect because an output manipulator function does not have to inherit from the ostream class. For example, the endl manipulator function does not inherit from the ostream class.