What inferences can you make regarding the ph of a particular part of the digestive system and the type and relative size of the carbon-based molecules that are broken down there?

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?