Final answer:
Amy is likely around 6 months old, as this is the age where infants typically begin to say babbling sounds like "mama" and "dada." Other behaviors indicating this age include sitting up with assistance, showing stranger anxiety, and having developed vision almost as sharp as an adult's.
Step-by-step explanation:
Based on the developmental milestones presented, Amy is likely around 6 months old. At this age, infants often engage in vocal play and may begin to pronounce two-syllable sounds such as "mama" and "dada." While each child's development can vary, six months is a common age for babies to demonstrate these behaviors. They also start showing physical abilities such as sitting up with support, grabbing objects, and showing the beginning signs of stranger anxiety. The development of acute vision nearly as good as an adult's and color discrimination are also key markers of this stage.
As infants approach 12 months, their vocabulary increases to potentially include several words, and they might start performing more complex physical tasks like standing or walking with assistance. At 24 months, toddlers considerably expand their language skills, capable of using many more words and beginning to form short sentences. However, the simple, repetitive vocalizations described, such as "mamamamama" and "dadadadadadada," are most indicative of the six-month stage.