The pair of organisms that can be in a parasite/host relationship is Dogs and fleas. In this relationship, fleas are the parasites that live on dogs (hosts) and feed on their blood.
The other pairs represent different types of relationships:
- Goats and Grasses: Generally a herbivorous relationship (goats eat grass).
- Snakes and Mice: A predator/prey relationship (snakes eat mice).
- Bees and Flowers: A mutualistic relationship (bees pollinate flowers while obtaining nectar).