A Geologist Observes Abundant Fossils of a Distinctive Trilobite Species

Multiple Choice

A geologist observes abundant fossils of a distinctive trilobite species in a shale,but this trilobite disappears as she walks through the shale.In younger rocks,just above the horizon where the fossil disappears another species of trilobite becomes the prominent fossil in similar shales.Which conclusion is most logical for this observation?

A) The organisms whose remains form the first fossil moved from the area for unknown reasons.
B) A hurricane or other catastrophe killed all of the early species so the other species could move in.
C) The second,trilobite group in the upper section went extinct where the change in fossils is seen.
D) The first trilobite species went extinct and its ecological niche was occupied by another species,which may have evolved from the first.