competitive commensalism mutualism parasitism
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: In a desert environment, cactus wrens often build their nests in cholla cacti to avoid predators. This behavior does not hurt the cacti. Which type of relationship do cactus wrens and cholla cacti demonstrate?
Possibilities:
- competitive
- commensalism
- mutualism
- parasitism

commensalism