The answer is a. To show that even seemingly eternal things are temporary,
When a sentence have two or more subjects

In the English language, the word "who" is almost always used as a pronoun.
It represents a person, similar to the words "I" and "me".
c. change someone's point of view
When you argue, what you are doing is trying to persuade someone to your way of thinking. This is why you may have heard the terms argumentative and persuasive (with regard to papers/essays) used interchangeably. Within this type of paper, what you will do is reason by way of presenting evidence in support of your point of view so that readers might, too, consider it.