When you CC someone on an email, their email address is visible to those who see the email. So, you should only CC those that absolutely need to see this email, or answer C. If you CC your boss and your boss’s boss on the wrong email, you could get a stern talking to. If you CC the whole world, you will probably lose some friends since they’ll be seeing everything and the kitchen sink in your life.
Everyone in the department may also land you in hot water in the same manner CCing your boss and your boss’s boss would. There are just some emails that need to be sent to one person and then forwarded, and then there are others that should just be shared with only a few specific people.