5.09 x 10 to the 6th power
The correct answer is (d.) proteins. Higher organisms use nitrogen to make their protein. Food that is containing protein also involves nitrogen in it. Protein also has amino acids that contain nitrogen in it which is a necessary essential nutrient for the body.
The 10% rule means that when energy is passed in an ecosystem from one trophic level to the next, only 10% of the energy will be passed on.
