hello doctors.my baby is 9 months old.he is crawling now, but not sitting straight ( sits in bending posting). now he crawls on his knees and trying to stand. but why till now he is not sitting?

A. a baby can sit without support around 8 months of age and baby start crawling around this most of the babies 9 to 10 months of age with standing with support your baby is having normal milestones