What is the main metaphor in the sonnet?

What is the main metaphor in the sonnet?

• A. The speaker's thoughts are like a journey or pilgrimage that continues even when the body rests.
• B. The speaker's thoughts are like a river that flows only when awake.
• C. The speaker's thoughts are like birds that fly away at night.
• D. The speaker's thoughts are like a lighthouse guiding him home.

Answer: (B)