Geologic time begins with a very long span called precambrian time. precambrian time ended about 544 million years ago. since then, the basic units of geologic time are, in order from longest to shortest: a) eras - periods - epochs. b) eras - epochs - decades. c) orders - epochs - periods. d) epochs - periods - centuries.

so the answer to this is eras-periods-epochs

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.