All the iron molecules that are in your body were originally created by

Explain why it’s important for scientists to study the sun. list at least two challenges researchers face when examining earth’s nearest star.

Explain what is meant by a river’s load, and describe how the load is carried.

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?