Author Question: Nearly 300 million years ago, dragonflies existed that were the size of large hawks today. Some ... (Read 25 times)

iveyjurea · **on:** Jul 16, 2018

Nearly 300 million years ago, dragonflies existed that were the size of large hawks today. Some scientists believe that these giants could fly then, but not today, because oxygen levels in the atmosphere were much greater.

If oxygen levels 300 million years ago were 50 higher than today, what percentage of the atmosphere would have consisted of oxygen for these giant dragonflies? A) 30
B) 20
C) 10
D) 2

Question 2

When you exhale, the major components of your breath include all of the following except

A) carbon dioxide.
B) nitrogen.
C) oxygen.
D) hydrogen.