I would say the second option, but that is a tough one.
Number 5 is the answer because it summarizes the topic of the paragraph.
The primary attribute of the characters in morality plays reflects the fact that these plays were naive allegories is the fact that the characters are often very simplified.
The theme of Robert Frost's poem is the destuctive potential of hatred and desire. In his poem, Frost explores with amazingly eloquent brevity two forces which have the potential to bring destruction to the world. The first of these two is desire, which Frost likens in heat and intensity to fire.
