In 1850 there was a large snowshoe rabbit population in Manitoba, Canada. Over the years, the winter coloration (the color of the rabbit's fur) of the surviving rabbit population changed. The graph shows the change in winter coloration of rabbits between 1850 to 2000. Based on the data, we could hypothesize that

Responses
A the winters are longer in length.the winters are longer in length.
B the amount of snow cover varied over the years.the amount of snow cover varied over the years.
C the snowshoe rabbit has migrated to another area.the snowshoe rabbit has migrated to another area.
D more snowshoe rabbit predators have moved into Manitoba.more snowshoe rabbit predators have moved into Manitoba.

B the amount of snow cover varied over the years.