What Is the Significance of the Fossil Archaeopteryx

What is the significance of the fossil Archaeopteryx ?

A) It establishes the time sequence of the transition from dinosaur to birds.
B) The bones of this animal were the first to be used for radiometric dating, which allowed the absolute age of the fossil to be determined.
C) It was the first fossil discovered from which both physiological and anatomical data could be gathered.
D) It was the first reptile-bird fossil discovered and helped to establish the relationship between birds and dinosaurs.