I don't really know but I pick b.have always been vestigial.
Answer:D
Explanation:All things are made up of atoms but only living things are made of cells.
The two membranes pull apart a little and create a small pocket or sack of air. As the developing bird grows, it breathes in oxygen from the air sack and exhales carbon dioxide. Several thousand microscopic pores all over the surface of the egg allow the CO2 to escape and fresh air to get in.
Please mark brainliest :)
Answer:
~What is the difference between primary and secondary consumers in a food chain?
~How does energy flow through the food chain?
~What's the most important part of the food web/chain?
~What role does a consumer play in a food chain?
~What is a decomposer and how does it play a part in the food chain/web?
~What does the food chain always start with?
~What is the difference between a food chain and a food web?
~What kind of question could you answer with a food web?
~What kind of question could you answer with a food chain?
~What is a secondary consumer, and why is it labled
as a secondary consumer?
Explanation:
Hope this helps!