The nurse is caring for a Sarah Newman, a 22-year-old female who is hospitalized with DIC following her spontaneous abortion. Sarah reports having pain in her knee joints. Following the administration of analgesics as ordered by the healthcare provider, which continual assessment does Sarah's nurse use to help monitor Sarah's pain?

a. Visual Analog Scale (VAS)

b. Glasgow Coma Scale (GCS)

c. Braden Scale

d. Numeric Rating Scale (NRS)