What command causes an eigrp router on as 5 to support authentication of the my_secure keychain with a key string of pep$r5?

a. ip authentication key-chain eigrp 5 my_secure
b. ip authentication eigrp 5 my_secure pep$r5
c. ip authentication eigrp 5 key-chain my_secure
d. ip authentication key pep$r5 key-chain my_secure

4. what is the reason for including the following code snippet in the header file animal.h? #ifndef animal_h #define animal_h class animal { public: animal(); animal(double new_area_hunt); void birth(); void hunt(double new_area_hunt); void death(); double get_area_hunt() const; private: double area_hunt; }; #endif