Final answer:
The increase in the number of psychological disorders identified by the DSM can be attributed to psychologists' improved differentiation among disorders, the availability of more psychologists and psychiatrists, and the increasingly stressful lives of people. Option d) is correct.
Step-by-step explanation:
The increase in the number of psychological disorders identified by the Diagnostic and Statistical Manual of Mental Disorders (DSM) from 60 in 1952 to over 300 in 1994 can be attributed to multiple factors. One reason is that psychologists have learned how to better differentiate among the various psychological disorders over time, leading to more accurate diagnoses.
Additionally, there are significantly more psychologists and psychiatrists available today compared to the past, which contributes to a higher identification rate of different psychological disorders. Lastly, the increasingly stressful lives of children and adults have also played a role in the significant increase in the number of psychological disorders.
Therefore, the best explanation for the increase in the number of psychological disorders is all of these factors - a) Psychologists have learned how to better differentiate among the various psychological disorders, b) There are significantly more psychologists and psychiatrists available to identify different psychological disorders, and c) The increasingly stressful lives of children and adults have led to a significant increase in the number of psychological disorders.