Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information. A. Ecosystems like the spruce ecosystem in Alaska tend to return to their previous states after disturbances such as pest outbreaks, fires, or major storm events. B. While ecosystems tend to return to their previous states after disturbances, the Alaskan spruce ecosystem might not if it is disturbed too often or too much. C. Ecosystems tend to return to their previous states after disturbances, so Alaska might again become covered with woodlands or grasslands. D. After certain types of disturbances such as pest outbreaks, ecosystems do not always return to their previous states but shift to being woodlands or grasslands instead.