&Como se demuestra la presencia de oxigeno en lo atmósfera con la práctica de la vela y el vaso

What two fields of study provide the core information that is used to classify organisms?

As a small change in a person's dna can cause a genetic disorder

Ialready know the answers to these questions and they are on the attachment. but i just need to know why that answer is the correct one. plz asap! this is for a report that i need to email by 10!