Fossils
Vestigial structures
Homologous structures
Molecular evidence
Comparative embryology
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Answer:
The correct answer would be D.Alveolar sacs are surrounded by thin capillaries where gases can be exchanged.
Alveoli are tiny sacs which form the site of gas exchange in the lungs.
The features of alveoli which help in gas exchange are:
- They increase the surface area in the lungs thus, more space is available for gas exchange.
- They have very thin walls, as thin as the thickness of a single cell only.
- They are surrounded by a bunch of thin capillaries which exchange gases with alveoli.
The actual answer is, "A", an ocean trench.
You can find out more about them by researching them up on Google, it's only a few phrases and a hit on the enter key :P
Answer:
C if you plug it into the sentance its the only one that makes sense
