If a scientist finds the remains of a plant between a rock layer that
contains 400 million-year-old Phacops fossils and a rock layer that contains
230 million-year-old Tropites fossils, how old could the plant fossil be?

Scientists can infer that the plant existed sometime from 400 million to 230 million years ago

the correct option is option d

answer: national resource conservation services

national resource conservation services is the us. based approach that provides technical and financial assistance for natural resource management. nrcs society in conservation of resources by involving in activities like farmland protection, flood prevention, watershed protection, urban conservation, conserves economic and environmental conditions. it conducts soil surveys and implements the policy of natural resources management on the society.