The nurse practitioner is assessing a 2-year-old patient for cognitive impairment. The best tool for detecting this impairment would be:

Rationale: A. Formal neuropsychological testing is more appropriate for older children who can follow complex instructions; it is not suitable for a 2-year-old. B. IQ tests require certain language and cognitive skills that a 2-year-old may not yet possess, limiting their utility at this age. C. Radiographic evaluation can identify structural abnormalities but does not assess functional cognitive abilities. D. Assessment of developmental milestones is the most practical and effective method for detecting cognitive impairment in a 2-year-old. Tracking language, motor, social, and problem-solving skills provides a reliable indication of cognitive development relative to age norms.