Final answer:
Talking to caregivers is the activity that best addresses the listening and understanding component for young infants, as it involves direct, responsive engagement that is essential for language development.
Step-by-step explanation:
Among the listed activities, talking to caregivers most effectively addresses the listening and understanding component for young infants. Research indicates that newborns have a strong auditory preference for human voices over other sounds and particularly for their mother's voice. Interaction with caregivers, such as being spoken to by family members, especially in a manner rich with intonation and rhythm (often referred to as 'motherese'), encourages the development of listening and understanding skills at a critical developmental stage.
Playing with musical toys can provide auditory stimulation but does not involve the verbal engagement that comes from personal interaction. Watching television is not recommended for very young infants as it lacks the two-way interaction necessary for language development. While reading books is beneficial and contributes to language development, the primary engagement comes from being read to by caregivers, where the listening and dialogue between the caregiver and the infant are central. Hence, the direct, responsive interaction of talking to caregivers is the activity that best supports listening and comprehension for young infants.