What is a "Climate system"?

Pls help and if you can explain

(1) which phrase describes an important agricultural change that occurred during the mississippian period? (a) first cultivation of wild grains (b) expansion of marsh elder farming (c) spread of corn agriculture (d) gathering of nuts and berries (2) which group of native americans use northwestern arkansas as it’s traditional hunting grounds? (a) osage (b) quapaw (c) woodland (d) caddo

When studying the calumet region of illinois and indiana alfred meyers noted four stages of development as new groups occupied this land in stage 2 farmers used the land primarily to grow food for their familes and their small communities

Ineed quickly! which of the following would not be considered an example of the transition of europe into the formation of larger nation-states? a. the hundred years' war b. the unification of italy c. the marriage of isabella and fernando d. the height of feudalism