The correct answer to this open question is the following.
The author's purpose or reason for writing this editorial was to inform and make people conscious about the terrible oil spill in April 2010in the Gulf of México, with the explosion of a British Petroleum rig. This spill caused so much damage to the ecosystem and the environment of the Gulf of México.
The two details from the text that support the answer are the following. The author, Kate Jackson, writes that the BP company knew about the possibility of an accident of this magnitude but it didn't do anything to prevent it. She said that David Rainey, an executive form British Petroleum, had assured the members of the Senate that the facility had no risk of a spill.
The other detail that supports the answer is that she wrote that the oil industry always had been aware of the dangers of spills but never has done so much to prevent them. Also, people like Robert Bea, an offshore engineer, had warned British Petroleum.
What quotes there is nothing there except the question
C. I found a bag of marbles.
This is the only sentence that contains an indefinite article. Indefinite articles are "a" and "an" for singular nouns. "some" is the indefinite article used for plural or uncountable nouns.
"the" is a definite article.
