Final answer:
At 9 months, a child reaches several developmental milestones, including walking with support, understanding object permanence, and engaging in social games like peek-a-boo.
Step-by-step explanation:
At 9 months, a child is reaching several developmental milestones. They can walk with hand-held support, demonstrate object permanence, enjoy games like peak-a-boo and bye-bye, and wave goodbye. These milestones indicate that the child is developing physically and cognitively.