You are given a sample of an unknown pure substance. To identify this substance, identify a property you could measure. Explain why measuring this particular property would be useful. My science work plz help Ill give 42 points

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?