Those who compulsively work are considered sick because compared to most people, they tend to
a. understand their wants and desires better
b. hold better paying jobs in technological fields
c. pay more attention to their loved ones’ needs
d. allow work to interfere with personal activities

Those who compulsively work are considered sick because compared to most people, they tend to allow for work to interfere with personal activities - d. This happens because they start postponing what they had to do in work to their home and for this reason they have less time for socializing and other activities. 

The one that most represents the earths mantle would be the skin since the mantle is the upper part of the earths depths which is just like the skin of an apple.