9. Danielle lives with her family on a farm. In school, she has been learning about the nitrogen cycle in science class. She knows that her father spread a nitrogen-based fertilizer on a patch of grass recently where the
Cows graze in the field. Why was it necessary to add a nitrogen-based fertilizer to the soil where there was a
patch of grass?
a. because nitrogen can only be "fixed" by lightning
b. because there are no decomposers on the farm
c. because bacteria released all of the nitrogen into the air
d. because plants cannot use "free" nitrogen