a woodpecker nesting in a cavity of a dead tree a tapeworm absorbing food in the digestive tract of a wolf a polar bear hunting a seal for food a hummingbird transferring pollen between flowers
I gave my students this multiple choice question: Which is the best example of a parasitic relationship?

Only one answer is correct among these 4 choices:
- a woodpecker nesting in a cavity of a dead tree
- a tapeworm absorbing food in the digestive tract of a wolf
- a polar bear hunting a seal for food
- a hummingbird transferring pollen between flowers

Could you tell me which one is correct?

a tapeworm absorbing food in the digestive tract of a wolf