How did the diploducus have babies?

Diplodocus, like other dinosaurs, reproduced by laying eggs. Female diplodocus would build nests to lay their eggs, which were likely similar to those of modern reptiles. After laying the eggs, the parents may have provided some level of protection, although specific behaviors related to nesting and caring for young are still a subject of research. Once the eggs hatched, the young would be independent, as is typical for many reptilian species.