ANSWER IN C++. Max 4 questions per Chegg rules. "One question per post- questions with sub-parts are fine, but posts with multiple questions will be closed."

5. What is a macro guard in a header file, and what is its purpose? Give a small Short Answers Section 2.3 The Header File and the Implementation File example as part of your answer 6. Suppose that the throttle class is implemented with a header file (throttle.h) and an implementation file (throttle.cxx), and that it is part of the namespace main_savitch 2A. Write the include directive and the using directive that are needed for a program to use the throttle class. 7. When is it appropriate to use a const reference parameter? Give a small example as part of your answer. 8. Suppose a function has a parameter named x, and the body of the function changes the value of x. When sss and Parameters Short Answers Section 2.4 should x be a value parameter? When should it be a reference parameter? With this function, could x ever be a const reference parameter