Arrange the following divisions of geologic time in order of decreasing size (i. e. the longest time period to the shortest time period) i epoch ii era iii period

The order, from the longest time period to the shortest time periord is: Era, Period, Epoch

Explanation:

In the geological time scale we have divisions that go from the longest tho the shortest: Eon, Era, Period and Epoch. The more recent Eon is the Phanerozoic Eon in wich we find 3 eras: Paleozoic, Mesozoic and Cenozoic. Each era has different periods, forme example, in the Mesozoic we find the Triassic, Jurassic and Cretaceous periods and finally each period has a division in epochs, those could be for example Lower, Middle and Upper.