The most influential book in mental health is

a. achieving the promise: transforming mental health care in america

b. healthy people 2020

c. the diagnostic and statistical manual of mental disorders, fifth edition

d. mental health: a report of the surgeon general

The correct answer is C. The diagnostic and statistical manual of mental disorders, fifth edition

Explanation:

Psychologists, psychiatrists, and other experts of mental health often rely on the last edition (fifth edition) of the "Diagnostic and statistical manual of mental disorders", which defines all disorders recognized by the American Psychiatric Association, establishes diagnosis criteria, and provides treatment recommendations.

This manual is highly relevant in the mental health field because the information is accurate and reliable, considering this is published by the American Psychiatric Association (an important organization in the mental health field in the U.S.), and it is the result of extensive research. Also, this helps experts in mental health to treat uncommon mental disorders or provide an accurate diagnosis. According to this, the most influential book in mental health is "The diagnostic and statistical manual of mental disorders, fifth edition".