They are replenished by sunlight. They are cycled through ecosystems. They are replaced by volcanic eruptions. They are produced constantly from nutrients.
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: Which of the following explains why elements, such as carbon and oxygen, that are used in organic molecules are not permanently removed from the environment?
Possibilities:
- They are replenished by sunlight.
- They are cycled through ecosystems.
- They are replaced by volcanic eruptions.
- They are produced constantly from nutrients.

They are cycled through ecosystems.