Final answer:
The phrase 'an imaginary bridge to life we would never fully know' best aligns with Option 3, indicating that the characters feel disconnected from a past that is beyond their understanding.
Step-by-step explanation:
The phrase 'an imaginary bridge to life we would never fully know' suggests a connection to something that remains out of reach or not fully understood. The characters are exploring the possibilities of a life or experiences that they can sense or imagine but can never completely grasp or experience firsthand. Here, the best explanation is that Option 3 is the most accurate: The characters feel the past is too far beyond their young imaginations. This implies a sense of distance between the characters and the past or the stories they have heard, indicating a separation by time and the understanding that some aspects of life or history will remain unknowable.