Which of the statements is true of the fossil record?

A)All of the stratified layers will be found anywhere a core sample is taken,except for human destruction.
B)Provided there is no uplifting,tilt,etc. ,the deeper the layer,the more recently it was laid down.
C)Once fossils are formed in a sedimentary layer,they are then protected from temperature and heat.
D)Fossil assemblages are important in identifying sedimentary layers and different layers have different assemblages of fossils.