"Flying down three thousands of feet, it is suspected that the Milky Way has set for nine days" comes from Li Bai's "Looking at Lushan Waterfall". The meaning of the poem is: the spectacular waterfall rushes down from a height, which really makes people doubt that it is the milky way pouring down from the sky. These two poems describe the majestic momentum of Lushan Waterfall. So, the answer to this question is a.