This age-old question really has a simple answer. Attempts to answer it, however, and attempts to get around implications of the simple answer are often quite convoluted.
What do you think about it?
I really agree with the eggs, because what?
Because I think the eggs existed at the time of the dinosaurs and hatch in the years after the dinosaurs, so the newly hatched chicks will adjust to the environment and over time the types of chickens appear to arrive at this time.