The line graph shows the estimated number of chipmunks in a state park on April 1 of each year from 1989 to 1999. The steepest downward slope on the graph represents which of the following?
The year with the fewest chipmunks
The period with the most rapid decline in chipmunk population
The period when the chipmunk population stabilized
The total decrease in chipmunks over the entire period
