Answer:a) prescribe medication.
Explanation: Prescription of medication is legally ordered by a health care or mental health care provider who has studied medicine or has a medical degree. Under mental health there is a psychiatrist and psychologist all who deal with mental issues but each plays a diffrent role , A psychiatrist is a medical doctor who specialises in mental health care service whilst a psychologist is not a medical doctor , their focus is on counselling people with mental related issues hence psychologist can not prescribe medication whilst a psychiatrist can prescribe medication.
"Josh has a doctoral degree in psychology and is a therapist in New York. " This means Josh is not a medical doctor but a psychologist so he can't prescribe medication.
On the other hand:
"His sister Sarah has a medical degree and is in a residency program for psychiatry" due to the that Sara has a medical degree she can prescribe medication.