The definition of compulsory is required by law or a rule; obligatory.
Answer:
C. Light as thistle-down and delicately tinted as wild-rose petals
Explanation:
Nature is simply the physical features of the earth which could include, plants, animals, the atmosphere and other attributes. When describing aspects of nature that made Alaska unique, John Burroughs described the mists as "light as thistle-down and delicately tinted as wild-rose petals". The mist is a part of nature so the description fits in.
In the same vein, he talked about the different shades of flowers with colors like, blue, green, rose and amber. He also described the seabirds which adorn Alaska. Also in the description of nature was the sea waves, soft winds and songs of birds.
