Explanation:

- The given phrase is about a feeling where someone emotionally wishes to return to a past time.

- Option 1: Emotion

- General term for feelings or psychological states.

- Too broad to fit the specific sentiment described.

- Option 2: Craving

- Desire or strong wish for something.

- Usually relates to physical wants, like food, not time periods.

- Option 3: Memory

- Refers to the act of recalling past events.

- Not necessarily tied to longing or strong emotional connections.

- Option 4: Nostalgia

- Relates specifically to a deep, wistful longing for the past.

- Perfect fit for the described sentiment.