Read the excerpt from Silent Spring. The roadsides, once so attractive, were now lined with browned and withered vegetation as though swept by fire.

In this excerpt, the phrase
best shows the author’s tone of despair.

withered vegetation

Explanation:

Rachel Carlson in her book "Silent Spring", has highlighted the degradation of the environment being done because of the excessive use of the pesticides. She builds her argument that the chemical industries have been deceiving people by giving incorrect information to them.  

In the given excerpt, the phrase 'withered vegetation' shows that the author is in a gloomy mood. She is upset to see the degrading environment. Her tone discloses her feelings of despair.

uncanny would be like unlucky or disaster. you can look for more in the dictionary or if you have text book then turn to a. 17 but it's different with textbooks.