biological combustion industrial lightning
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: In order for nitrogen to be used for growth in organisms, it must be "fixed." When nitrogen is "fixed," it is combined into the form of ammonium or other nitrogen ions. During which type of fixation do organisms and nitrogen interact?
Possibilities:
- biological
- combustion
- industrial
- lightning

biological