I believe your answer would be Echinoderms and Chordates. I hope this helps!
Answer: C. there is more silicon than calcium at the surface of the earth
Explanation:
There are many ways you can reduce power consumption.
You can take shorter showers, turn of your lights before leaving the house, using less appliances. If you need more, comment below. Hope this helps..
One good reason would be that they could give someone, or many people who are in desperate need of a new organ, a second chance at life.