A natural right is any right that exists by virtue of natural law. So a sentence could be "The First Amendment illustrates natural laws such as the freedom of speech, petition, and religion."
I could tell by the way the teacher was scowling that I didn't have the right answer.
He has a natural ability for drawing.
It is NATURAL to have two eyes.
She wishes she could be ambidextrous so she could give her right arm a break from steaming
Your question is itself a sentence which uses the word "could".
The sentence could be correct if it followed a context sentence such as "Changing where the water is poured could help one plant to live." Otherwise, the word "but" makes this a dependent clause, not a sentence.
natural
The emergence of our protective eyelid was a byproduct of natural law. "natural law" is a phrase, not a word.
The word is put in a sentence like I just did right now.
It is imperative that you take the cat to the vet right away, or he could die.
These chores on the left column are for you to do and these on the right are for me to do. These are the only ones I could find. (see the related link)
This is the right way to answer a question.