What is a hormone?
a. it is a gland that is produced by the endocrine system
c. it is a chemical messenger that is produced by the excretory system
b. it is a chemical messenger that is produced by the endocrine system
d. it is a chemical messenger that is produced by an exocrine gland

Option B (it is a chemical messenger that is produced by the endocrine system)

Explanation:

Hormones can be defined as the product of endocrine glands which help in the regulation of physiological and behavioral activities like metabolism, growth, development, stress management, tissue functions and many more.

Endocrine glands are governed by the endocrine system. Endocrine glands releases hormone directly into the bloodstream instead of ducts.

Therefore, the correct answer is "Option B".

step 1 ammonium can be absorbed by plants, but some is converted into nitrates which are better for plants to absorb. this is called nitrification. 2. step 2 the deer eats the plants and uses the nitrogen-containing proteins for cell growth. 3. step 3 bacteria in the soil conduct nitrogen fixation to convert nitrogen gas from the atmosphere into ammonium. 4. step 4 some of the nitrates are absorbed back into plants, but denitrification breaks down the nitrates into nitrogen gas released back into the atmosphere. 5. step 5 nitrogen is found in the urine, which gets broken down into ammonium through the process of ammonification. 6. step 6 plants absorb the ammonium and begin assimilation, the process to add the nitrogen to protein.