Which of the following statements are correct about Harappan seals?

1. Harappan seals often depicted animals such as unicorns and bulls.
2. The seals were primarily used for religious rituals.
3. Seals with inscriptions have been found at multiple Harappan sites, including Harappa and Mohenjodaro.
4. Harappan seals have been found in Mesopotamia, suggesting a trade relationship between the two civilizations.