Ask them to suggest one of the roles plants play (other than holding the soil together and stopping erosion) in a catchment area i.e. cycling water [Growing plants use water and expel it through their leaves and consequently water is lost to the atmosphere and may become clouds then rain].
(them; to suggest; one of the roles) (Growing plants; use; water) (water; may become then; clouds) (the roles; play; plants) (Growing plants; expel; it)
them Growing plants water the roles Growing plants
to suggest use may become then play expel
one of the roles
water
clouds
plants
it