Final answer:
Observing an infant's motor skills and sensory responses is a primary procedure used to measure their development. This includes tracking physical abilities and reactions to sensory stimuli to assess their growth and ensure typical progression through developmental milestones.
Step-by-step explanation:
One procedure used to measure the development of an infant is B) Observing the infant's motor skills and sensory responses. This method involves monitoring the progression of physical abilities, such as the ability to hold up the head, sit with assistance, crawl, and eventually walk, as well as the infant's reactions to various sensory stimuli.
Within the first year, infants undergo significant growth in both motor skill areas and sensory abilities. Motor development, for example, typically follows an orderly sequence, while sensory abilities allow infants to navigate and understand their environment. These areas of development, along with cognitive skills, are observed to assess the overall progression of an infant's abilities. It is important for the pediatrician to understand the context of an infant's development, including whether the individual's developmental milestones align with the typical progression or if there are any factors that may account for deviations from the norm.