<span>forgoing worldly possessions is the correct one</span>
Hey Friend!
DESTITUTE in this case, (and many others) means:
'lacking possessions or resources'
Usher's madness begins to increase because he can hear the sound of Madeline below.
Even though his sister is buried in the basement, he can constantly hear her scratching her coffin. He was tortured by these sounds until the protagonist came to visit him so he could share his troubles with him. Usher is afraid of his 'undead' sister and of dying himself, which is why he grows crazier and crazier by the day, until he is finally killed by his own sister in the end.
It's not clear where the paragraph break is between one and two, but I might be able to help you. The last option is incorrect, because all of the text relates which is why it's hard to determine where the paragraph break might be. Paragraph one does not offer a solution as it isn't until the end we know the cause of the dark day. While both paragraphs have at least one fact, paragraph one seemingly is full of guesses as to the cause of the dark day. This leaves the only correct option as the first one. The researchers decided to investigate the cause of the dark day, and then the results are reported.