多选题 As Gilbert White, Darwin, and others observed long ago, all species appear to have the innate capacity to increase their numbers from generation to generation. The task for ecologists is to untangle the environmental and biological factors that hold this intrinsic capacity for population growth in check over the long run. The great variety of dynamic behaviors exhibited by different populations makes this task more difficult: {{U}}some populations remain roughly constant from year to year; others exhibit regular cycles of abundance and scarcity; still others vary. wildly, with outbreaks and crashes that are in some cases plainly correlated with the weather, and in other cases not.{{/U}}
According to the passage, all of the following behaviors have been exhibited by different populations EXCEPT:

• A. roughly constant population levels from year to year.
• B. regular cycles of increases and decreases in numbers.
• C. erratic increases in numbers correlated with the weather.
• D. unchecked increases in numbers over many generations.
• E. sudden declines in numbers from time to time.