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