The diagram below shows the layers in a rock having a brachiopod:
Which statement about the rock fossils is true?
Organism X existed for a short period of time.
Organism Y became extinct before organism X.
Organism X and organism Y existed at the same time.
Organism Z became extinct much before organism X.
A, organism X existed for a short period of time. The organism is only found within a specific layer and never seen again. That is, I'm assuming Z is near the top of the time scale.
