丽红近日流鼻涕、打喷嚏、咽喉肿痛，医生说她患了流行性感冒。你知道这种疾病是由什么引起的吗？                                                                                                                                                                                                                                                                  

A.SARS病毒           B.HIV病毒        C.流感病毒       D.天花病毒