As a vertebrate, embarrass develop, they go through a series of 23 stages. Which statements about these stages are correct select the two correct answers.

Stages are identified by age and size of the embryo
The stages are identified by the structure that develops
All vertebrates go through all of the stages
All vertebrates go through the same stages at the same time

The correct statements are:

- The stages are identified by the structure that develops
- All vertebrates go through all of the stages