Final answer:
By 9 months, infants may not yet consistently respond to verbal requests or show a wide range of emotions and stranger anxiety, as these milestones typically solidify closer to one year. Developmental milestones can vary among infants, and consultations with a pediatrician are advised for concerns.
Step-by-step explanation:
By 9 months of age, certain social emotional milestones likely have not been met by infants. For instance, responding to verbal requests such as "wave bye-bye" or "blow a kiss" may not be consistently demonstrated until around 9 to 12 months. Also, while a sense of object permanence and behaviors like shaking the head "no" are expected to develop around 6 to 9 months, more complex social emotional responses such as expressing a wide range of emotions, understanding simple requests, and showing definitive signs of stranger anxiety could still be emerging and solidifying in the period up to the first year.
It is important to remember that developmental milestones can vary significantly among infants. If there are worries about a child's development, it's best for caregivers to consult with the child’s pediatrician.