Final answer:
Around six months of age, infants start developing several motor and sensory skills, including the ability to pick up objects, sit up, and discriminate depth. They also begin to make two-syllable sounds and show anxiety toward strangers.
Step-by-step explanation:
Around six months of age, an infant is normally able to pick up objects and transfer them from hand to hand. They can also pull themselves into a sitting position. Their vision will have improved so it is now almost as acute as adult vision. The infant will also start noticing colors and start to show the ability to discriminate depth. They are likely to enjoy vocal play and may start making two-syllable sounds such as "mama" or "dada." They may also start to show anxiety toward strangers.