Answer:
D. Nature is constantly changing.
Step-by-step explanation:
The phrase "line her hardest hue to hold" likely refers to the idea that nature is constantly changing and evolving. The word "hue" can refer to the color or appearance of something, and the phrase "hardest hue to hold" suggests that it is difficult to maintain or preserve this appearance or color. This suggests that nature is in a state of constant change and that it is difficult to hold onto any particular aspect of it for very long. The phrase "mostly" might be used to emphasize this idea and to suggest that change is a central characteristic of nature.