Which of the following can be said about the use of agriculture?
a. it bears no effect on the environment.
b. it stunted the growth of civilization and development.
c. it prohibited the use of machinery.
d. it has included practices that led to pollution of soil and water.

Amino acids contain the elements carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. of the 20 amino acids found in humans, 11 are called "nonessential" because they can be manufactured by the body when needed. which elements in these 11 amino acids are commonly obtained from the metabolism of sugar molecules?