Answer:
C. They pollinate the flowers that only open at night.
Explanation:
A niche is the functional role an organism performs in the ecosystem. Simply, the question is asking for the role of nocturnal animals as pollinators.
Nocturnal animals are animals that are very active at night. This is an evolutionary advantage for them because there is less danger at this point of the day.
Therefore, some nocturnal animals can help to pollinate flowers that only open at night.