题目选项分析

A report on acid rain concluded, " Most forests in Canada are not being damaged by acid rain." Critics of the report insist the conclusion be changed to, "Most forests in Canada do not show visible symptoms of damage by acid rain, such as abnormal loss of leaves, slower rates of growth, or higher mortality.

"Which of the following, if true, provides the best logical justification for the critics' insistence that the report's conclusion be changed?

【选项】All forests in Canada have received acid rain during the past fifteen years.