That crocodiles share a common ancestor with bird dolphins and dog support your answer?

That statement is incorrect. Crocodiles, birds, dolphins, and dogs do not share a common ancestor in the way you're implying. Here's why:

* Crocodiles and Birds: Crocodiles and birds share a common ancestor that lived millions of years ago. This ancestor was a reptile, and both groups diverged from this lineage. This is why crocodiles are sometimes referred to as "living dinosaurs" – they are the closest living relatives to dinosaurs.

* Dolphins: Dolphins are mammals, and they evolved from land-dwelling mammals that returned to the sea. This means that their lineage diverged from the ancestor of crocodiles and birds much further back in time.

* Dogs: Dogs are also mammals, and their lineage diverged from the ancestor of dolphins even further back in time.

In Summary:

The evolutionary relationships are more complex than a simple "common ancestor" for all these animals. Here's a simplified diagram:

* Ancient Reptilian Ancestor --> (Branch A) Crocodiles, Birds

* Ancient Mammalian Ancestor --> (Branch B) Dolphins, Dogs

It's important to understand that evolution is a complex process with many branches and divergences over millions of years.