For example, the air which we breathe is a gas composed principally of two elements, oxygen and nitrogen.
(the air; breathe; we) (the air which we breathe; is; a gas composed principally of two elements, oxygen and nitrogen) (a gas; composed principally; of two elements, oxygen and nitrogen)
the air the air which we breathe a gas
breathe is composed principally
we
a gas composed principally of two elements, oxygen and nitrogen
of two elements, oxygen and nitrogen