2. Decide if the following statements are true () or False (x) : a. To use a predefined function in your C++ program, you must include its prototype. b. Value returning functions must include a return statement. c. Void functions can be used to return multiple values given multiple reference parameters. d. The standard C++ library iostream is used to read and write from files. e. A global variable is recommended because it has no side effect on the instructions elsewhere in the program that use the global variable