Final answer:
Juliet's line 'My only love sprung from my only hate!' shows her understanding of Romeo's identity as someone from the rival Montague family.
Step-by-step explanation:
The line from Juliet that best shows she understands Romeo's identity is: My only love sprung from my only hate! This line demonstrates Juliet's recognition that her love for Romeo has developed despite him being from the rival Montague family, which is her family's 'only hate.' It reveals her understanding and acceptance of the conflict between their families and their forbidden love.
Learn more about Characters and Conflict in Romeo and Juliet