Behind on milestones?

Kaitlin
At my baby's 4 month appointment, the nurse asked these questions:
Is she rolling over?
Is she laughing?
Is she passing objects from one hand to another?
My answer to all of them was no. I didn't think my baby was behind, but I guess so? She rolls onto her side, but can't quite flip yet. She's a talking/interacting fool, just not laughing yet. She is good at reaching/grasping/bringing to her mouth, but can't switch from one hand to the other yet.