Answer:
The correct answer is option C.
Explanation:
Influenza C virus is the member of genus Influenzavirus C which causes influenza just like other influenza viruses. These viruses are known to infect pigs and humans. Type C species caused flu is rare in comparison to Types A or B.
Other common influenza viruses A and B also cause seasonal infestation every year because of their ability to shift antigenicity. Influenza virus C does not have this ability to antigenic shift and not considered as a concerned threat to human health. Because of this, it is rarely included in vaccinations against influenza virus C.
Thus, the correct answer is option C.