15. Emphasizing the preservation of entire ecosystems will
a. cause the economic needs of farmers to suffer
in order to save a single species.
b. decrease biodiversity, especially in tropical rain
forests, coral reefs, and islands.
c. throw the food webs of many ecosystems out of
balance.
d. save many unknown species from extinction.

The correct answer is "Nitrogen will only become available to other, nearby plants when the nodules or the nitrogen-fixing plant itself dies".

Explanation:

Nitrogen fixing bacteria maintain a symbiotic relationship with plants. Bacteria performs nitrogen fixation providing the plant with ammonia, while bacteria has a safe place and nutrients to prosper. This relationship is very intimate because it occurs at the root hair of the plant at structures called nodules. Therefore, nitrogen will only become available to other, nearby plants when the nodules or the nitrogen-fixing plant itself dies