Final answer:
Infants develop significant skills between 6 and 12 months, including teething, sitting without support, and beginning to say their first words like 'mama' and 'dada.'
Step-by-step explanation:
Infants begin saying their first word, sitting without support, and teething at 6 to 12 months. By 6 months, infants are typically babbling, have the ability to sit and may start crawling, with their deciduous teeth starting to come in. By 12 months, they may be saying first words such as “mama” or “dada”, can usually stand with help, and may have begun walking.
Notably, at six months, the baby's vision is almost as sharp as adult vision, and they may also start showing stranger anxiety. As they near one year, their understanding of simple commands and words increases, and they begin to exhibit more complex behaviors like mimicking actions and experiencing separation anxiety while forming attachments to their parents.
In summary, the developmental milestones from 6 to 12 months are significant, marking transformations in mobility, vocalization, and social interaction.