. According to the article, how has
observing the decline of big trees most
affected the author?
A
A. He became active in reducing carbon
emissions in order to protect big
trees.
B. He expanded his previous research of
American big trees to become a global
study.
C. He expanded his research, intending
to further explain and publicize the
causes of big trees' decline.
OD. He was relieved and encouraged by
people's enthusiasm to protect big
trees and the environment.