How many languages are there? (even the ones who say don't exist anymore)

Which best summarizes what scientists learned about how microbes benefit the human body? they are part of a normal human ecosystem. they have become less harmful to humans than they used to be. they process nutrients, fight disease, and accommodate change. they humans overcome the effects of antibiotics.`

What is a form of systematic musicology

What is the longest word in the world? this is grammar.