One problem facing plants and humans is the fact that the earth tilts on its axis, changing the length of the day during the year.
(One problem; facing; plants and humans) (One problem facing plants and humans; is; the fact that the earth tilts on its axis) (the earth; tilts; on its axis)
One problem One problem facing plants and humans the earth
facing is tilts
plants and humans
the fact that the earth tilts on its axis
on its axis