What is the approximate percentage of oxygen in expired air?
A 0.04% B 4% C 16% D 21%

There are only about 250,000 known fossil species. true or false

Which statements explains what the fossil records indicates? check all that apply. a) earth is 4.5 billion years old b) many organisms have become extinct c) mammals have always existed on earth d) mass extinctions have occurred several times on earth e) the amount of water on earth has decreased over time?

Identify the product of genetic engineering.