Which of the following is true about the gross motor function growth curves for children with Down syndrome?

The assertion that 78% of children with Down syndrome are able to sit by 12 months is accurate based on developmental milestones observed in this population. Sitting is typically one of the earlier gross motor skills achieved, and research shows that while children with Down syndrome may experience delays, a significant majority reaches this milestone by their first birthday.

Acquiring the ability to sit independently is crucial as it serves as a foundation for further gross motor skills like crawling and eventually walking. While there is variability in motor development among children with Down syndrome, the statistic points to a majority achieving this important milestone, thus reflecting their developmental trajectories more positively compared to some other skills.

The other statements present figures that either underestimate or do not align with typical observations relating to children with Down syndrome and their gross motor skill development, with walking and running milestones typically occurring later than those mentioned in options A, C, and D.