C? Least useful information, and includes an opinion, both uncomforting and personal.
Hi Daralava,
How does the troposphere differ from the stratosphere?
There are 2 major difference between the troposphere and the stratosphere, which is that the stratosphere is higher located than the troposphere, also the stratosphere is also warmer becase it receives more solar radiation the the troposphere.
The correct answer is - the first, black layer.
If the situation is that the rock layers have not been disturbed, and their alignment is in order as the periods in which they have been on the top, before being covered with new sediments, than the oldest fossils will be at the bottom layers, will the newest in the top layers.
In this situation, we know that the mollusks have evolved before the arthropods, and since the arthropods are found in the second, grey layer, the mollusks will be found in the layer bellow them, the first, black, layer.