Because it requires lots of "emotional labor," customer service has been called

A) a spiritual quest.
B) the lost art.
C) mission impossible.
D) a performing art.
E) the world's toughest job.

Customer service requires a significant amount of emotional labor, which involves managing one's emotions to meet the emotional demands of customers. This can be compared to a performing art, where one has to put on a show or performance while managing their emotions to meet the expectations of the audience. The other options, such as "spiritual quest" or "mission impossible," do not accurately convey the nature of emotional labor involved in customer service.