Answer:
The correct answer is heights.
Step-by-step explanation:
In this line of "Song of Myself," steeps is used as a noun as indicated by the article "the." Steeps as a noun means high areas, like high mountain reaches and areas that are of great heights. This seems to be the meaning of steeps in the poem because the verb that precedes the noun is "descends." Therefore, it makes sense that "the steeps" is used in its noun form and that it means something with great height.