Answer:
The correct answer would be - lipids.
Explanation:
Many aquatic birds secrete a waxy organic substance which coats their feathers and this substance allows their feathers to repel the water which is helpful for their flying even after floating in the water.
An analysis of these substances would tell that these substances are composed of lipids as lipids are the only macromolecules that are hydrophobic which means they try to avoid water and not allow water to pass through them.
