Polar bears depend on sea ice, which melts during exceptionally warm weather, for access to food. When warm weather lasts longer than normal, polar bears accumulate fat—energy stored for their long winter hibernation—more slowly and weigh less, on average, as a result. At the same time, during periods of prolonged cold, polar bears weigh significantly less than they usually do, on average.
Which of the following, if true, does most to explain the contrast described above?
【选项】
During periods of prolonged warmth, polar bears have to compete with a wider variety of species for the same food sources.
选项是否正确？