I would say the answer is B.) There is data at this digit's location, although I have to admit I am not completely sure, nor really educated in this area. Sorry I couldn't be of more help. :)
I believe the answer is the first one, scientists must know the layers of rock, for example, a fossil was found in bedrock, The scientist should know the types of rock in it all together. hope this helped!
Answer:
Just took this - it is: by observing cellular respiration under the absence of light.
Explanation:
Decomposers feed on dead organisms.