They are among the most important groups of animals on land because they play a vital role in breaking down dead plant material.
(They; are; among the most important groups of animals on land; because they play a vital role in breaking down dead plant material) (they; play; a vital role; L:in breaking down dead plant material)
They they
are play
among the most important groups of animals on land because they play a vital role in breaking down dead plant material
a vital role L:in breaking down dead plant material