The assessment method that would have the most validity and reliability would be:

A) the MMPI (Minnesota Multiphasic Personality Inventory) .
B) the Rorschach Inkblot Test.
C) tests using doll play to determine whether a child has been sexually abused.
D) clinical observations and interviews.

The MMPI (Minnesota Multiphasic Personality Inventory) is a standardized psychometric test of adult personality and psychopathology. It is widely used and considered to have high validity and reliability among psychological assessment tools. The Rorschach Inkblot Test, tests using doll play, and clinical observations and interviews are more subjective and can vary significantly in interpretation and outcomes, making them less reliable and valid compared to the standardized and empirically validated MMPI.