Which of the following describes the function of the M2 protein from influenza virus?

A) It induces the fusion of the viral envelope with the cell membrane.
B) It binds to the host cell receptor for viral entry.
C) It acts as an ion channel to allow H+ ions to enter the virion.
D) It helps to initiate transcription of viral mRNAs.
E) It cleaves off the 5' caps from the cellular mRNAs.