In 1944, reindeer were introduced to an optimal habitat on st. matthew island in the bering sea. the population grew exponentially until the winter of 1963-64, when the population dropped dramatically. the presence of may have maintain the population of reindeer.
i think it's a

It seems that you have missed the given choices for this question, but anyway, the correct answer is FEMALE REINDEER. In 1944, reindeer were introduced to an optimal habitat on St. Matthew Island in the Bering Sea. The population grew exponentially until the winter of 1963-64, when the population dropped dramatically. The presence of FEMALE REINDEER may have helped maintain the population of reindeer.

The correct answer is b