Final answer:
The most likely task for a developmental psychologist is to study the psychological crises people experience at different ages, as it aligns with their goal of understanding psychological changes throughout a person's lifespan.
Step-by-step explanation:
Developmental psychology is concerned with the scientific study of changes that occur in human beings over the course of their life. A developmental psychologist might take on tasks such as designing research studies, conducting experiments, or developing intervention programs that address various life stages from infancy through old age. When it comes to the activities a developmental psychologist is most likely to engage in, they could be focused on any aspect of human growth including physical, cognitive, and psychosocial development.
Given the options, a developmental psychologist would most likely study the psychological crises people experience at different ages. This is because developmental psychology is fundamentally oriented towards understanding the progression and changes in psychological attributes throughout the entirety of a person's lifespan, considering domains that include physical, cognitive, and psychosocial development.
A high school graduation test's predictive validity for college success typically falls more within the realm of educational or school psychology. Designing programs to help people avoid risky sexual behaviors might be more aligned with health psychology while studying how prejudice develops could be a focus within social psychology. Therefore, given the context of developmental psychology, focusing on psychological crises at various stages of life is the most fitting activity among the offered choices.