In
the
____________________
____________________
food
is
broken
down
into
small
parts
called
____________________
.
Undigested
food
forms
____________________
.
Air
contains
a
gas
necessary
for
living
things
called
____________________
.
Oxygen
passes
to
our
body
through
the
____________________
which
are
the
organs
in
the
____________________
system
.
