Fossils in precambrian rocks are rare, while there are many fossils in rocks from the phanerozoic eon. what does this evidence suggest? a. there was a major change in the diversity of life in the phanerozoic eon, probably due to mass extinction. b. there was no life in the precambrian eon. c. the rocks from the phanerozoic eon are much harder than those from the precambrian eon. d. there was no change in the diversity of life in the phanerozoic eon.