Answer: The word X represents the organs which is no longer used by the species.
Explanation:
The word vestigial shows the characters that is not used by the species anymore. Example is appendix which is considered as a vestigial organ in human beings as it is no longer useful for the human body.
This organ was used when there was only vegetarian food available for the human beings to eat.
But now that animals and vegetable both are available there is no need for the enzyme required the digestion of cellulose.
So, this organ is vestigial for the human body.
Brine rejection is a process that occurs when salty water freezes. The salts do not fit in the crystal structure of water ice, so the salt is expelled.
Erosion, pollution, and global warming
A) Algae.
(im not 100% sure but it makes the most sense to me. See if google knows to double check)
