Final answer:
The correct answer is 'b. medium' for a steak that is well done on the outside and has a reddish-pink hot center.
Step-by-step explanation:
When a guest requests that a steak be cooked medium, the outside will be well done, dark brown with a reddish-pink hot center. The option 'b. medium' fits this description of steak doneness. Cooking a steak to a medium temperature typically involves reaching an internal temperature of around 145°F to 160°F. This level of cooking ensures the outside is well-seared and dark while keeping the center warm and reddish-pink.