Curious as to why you separated the Carboniferous Period into its subdivisions. Was pretty obvious what they were when there were 2 left between D and P, but still seemed an odd non sequitur.
Only in the US is the Carboniferous Period subdivided into the Pennsylvanian and Mississippian, which are also called 'Periods' - very confusing. Suggest the question is amended to reflect this and how the rest of the world views this Period of geological time - ie only as the Carboniferous Period.
I have to agree with the previous several comments. Your categories aren't consistent. you have eras mixed in with epochs mixed in with periods. It's confusing and impossible to complete with 100%.
otherwise great quiz c: