Final answer:
It is false that fclose in Octave/MATLAB can only close successfully opened connections; fclose can attempt to close any file identifier but will return an error if the identifier is invalid or already closed.
Step-by-step explanation:
The statement that the fclose function in Octave/MATLAB can only be used to close a connection that has been successfully opened is false. The fclose function can be used to attempt to close any file identifier, including invalid or already closed ones. In such cases, fclose will return an error status, but the function call itself is valid and can be executed. It's important to note that attempting to close an invalid file identifier is not a recommended practice and usually indicates the need for better error handling in the program.