A. TRUE OR FALSE. Write TRUE if the statement is valid and FALSE otherwise. Write your answers in a separate paper. 1. Precambrian Time represents 90 percent of geologic time. 2. Human ancestors developed during the Paleozoic era. 3. The boundaries between the periods of the Cenozoic are marked by mass extinction. 4. Organisms in Precambrian Time has soft bodies with no shells or skeletons. 5. Eon is the second longest time; measured in hundreds of millions to billions of years.