2fe(s) + o2(g) → 2feo(s)

to which category does this reaction belong?

Redox reactions

Explanation:

Redox reactions consists of both oxidation and reduction

one species gets oxidised and other species become reduced, both oxidation and reduction happen simultaneously

reduction is either gain of electrons or gain of hydrogen. in reduction the oxidation number of species reduces

in this reaction the reduction half equation is

O₂ + 4e --> 2O²⁻

oxidation is either loss of electrons or gain of oxygen. in oxidation the oxidation number of species increases.

Fe --> Fe²⁺ + 2e

since both these half reactions happen overall its a redox reaction

d.) circle motion requires a force to give it a centripetal acceleration.

tracks, burrows, eggshells, nests, tooth marks, or gastroliths