Read the paragraph from the introduction [paragraphs 1-3].
If the keystone species disappears from the ecosystem, no other species can do its job. The ecosystem would have to radically change, allowing new and possibly invasive species to take over the habitat.
Which of the following words, if it replaced "radically" in the second sentence above, would CHANGE the meaning of the sentence?
A. thoroughly
B. completely
C. drastically
D. beneficially