How many amino acids are considered "essential" because they cannot be made by the body and must be supplied by food?

A) 2
B) 9
C) 11
D) 20
E) 22

There are 9 essential amino acids that the human body cannot synthesize on its own and must obtain from dietary sources. These include histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.