Answer to Question 1
More than half of the amino acids are nonessential amino acids, meaning that the body can make them for itself. Proteins in foods usually deliver these amino acids, but it is not essential that they do so. There are other amino acids that the body cannot make at all, however, and some that it cannot make fast enough to meet its needs. The proteins in foods must supply these nine amino acids to the body; they are therefore called essential amino acids. (Some researchers refer to essential amino acids as indispensable and to nonessential amino acids as dispensable.)
Answer to Question 2
d