At about 9 months of age, which gross motor milestone is typically achieved?

• A. Stands briefly with support but cannot sit independently.
• B. Sits without support and may crawl or pull to stand; cruising may begin.
• C. Walks independently across a room.
• D. Lifts chest and extends arms while prone.

Answer: (B)

Around nine months, the trend is toward stability plus the onset of mobility. Infants at this age typically sit without support, using their trunk control to stay upright. From that stable base, they begin to move in two common ways: crawling on hands and knees or pulling to stand, with some starting to cruise along furniture. This combination—independent sitting with the potential to crawl or pull to stand and possibly cruising—fits the nine-month stage best.

Other options describe earlier or later milestones: standing briefly with support but not sitting independently suggests less-developed trunk control for this age; walking independently usually comes closer to or after the first birthday; and lifting the chest and extending the arms while prone is a milestone from earlier infancy.