Mosty likely it is none of the above .
So its acquired immunity and the cells responsible are the B lymphocytes that produces antibodies against the virus. Memory is keep since first encounter of the virus by the immune system by way of the antibodies that was initially produced. The antibodies are there already, which makes it fast to act upon when expose again.
Answer:
Covering mouth while sneezing
Explanation:
It prevents germs going airborne and spreading to another person or surface.
The other answers are ways to get better from an illness or are just inefficient
That would be cardio work
