Final answer:
The book in which Theory X and Theory Y were first explained is The Human Side of Enterprise (option B).
Step-by-step explanation:
The book in which Theory X and Theory Y were first explained is The Human Side of Enterprise (option B).
The theories were first proposed by Douglas McGregor, a social psychologist, in his book published in 1960.
McGregor argued that there are two contrasting sets of assumptions about human nature, and these assumptions underlie two different management approaches: Theory X and Theory Y. Theory X assumes that people are inherently lazy and need to be controlled and coerced to work, while Theory Y assumes that people are self-motivated and can be trusted to take responsibility and contribute to the organization's success.