A. I know the answer is C but I really have an issue with this one. While I understand the underlying concern for Mayo, I think this rule is too broad. For example I have been in my career for 29+ years, and only the last two years has been with Mayo. This rule means that I can not endorse any individual I worked with at ANY job prior to coming to Mayo. I think people understand that at LinkedIn it is not an endorsement by my current employer if I endorse a former colleague I worked with, or a skill that I witnessed that colleague using at 'XYZ' company years before joining my current employer. Mayo should not own my career.
Appropriate or not, Linked in thinks it's a great idea. I think it's rather meaningless, (though it's nice too see those endorsements add up) because you're already demonstrating that you have x, y, z skills in your work/education sections in your profile. I think the feature is a little fluffy and made really as a way for Linked in to increase "engagement" among members.