SARS-CoV-2 is mainly transmitted through respiratory droplets when an infected person sneezes, coughs, or talks. How might this relate to the size and/or structure of viruses

What are the four basic classes of organic molecules how do they differ structurally and functionally

The pharynx is the structure in the body that serves as a pathway of both air and food. how does the body make sure that food does not get into the lungs? the salivary glands secrete enzymes that pull food out of the air pathway. the small intestine pushes the air out of the digestive system. the pancreas breaks down food in the air pathway. the epiglottis closes the air pathway so that food will not enter it.

How can antibodies "remember" a particular bacterial invader or "antigen" on that invader?