单项选择题

Questions 4 to 7 are based on the following conversation. At the end of the conversation, you will be given 20 seconds to answer the questions. Now listen to the conversation. According to the professor, why is the buffalo population increasing

A.More buffalo are surviving the winter.
B.Fewer buffalo are dying of disease.
C.More buffalo are being born.
D.Fewer buffalo are being killed by hunters.