Why do sedimentary rocks have layers of different colors sometimes?

Which country is currently the most populated country in the world? a. india b. china c. mongolia d. indonesia

In the following diagram, four different index fossils are labeled: which of the labeled fossils comes from the oldest organism? a b c d

If you were a casual recreational hiker with young children, which of the following trails would be least strenuous for a leisurely family outing? a. merced lake trail b. mirror lake loop trail. c. tenaya lake and tuolumne meadows trail d. el capitan trail