Consider the following statements regarding burial practices in Harappan sites of Punjab:

1. The burial practices at Ropar suggest that the dead were buried with grave goods like pottery and ornaments.

2. At some sites, dogs were buried along with humans, indicating possible ritual significance.

3. The cemeteries discovered at Harappa and Ropar show evidence of extended burials.

4. Unlike Mesopotamian civilizations, the Harappans built large tombs for their rulers.

How many of the above statements are correct?