Most Vegetarians Have to Watch Their Diet Closely and Eat

Most vegetarians have to watch their diet closely and eat certain foods in combination, like lentils and corn, to obtain all of their essential amino acids. Which of the following statements is the BEST explanation of why this is so?

A) Lentils are a food high in protein, therefore eating lentils is a good alternative to eating meat.
B) Eating meat provides all eight essential amino acids; because vegetarians don't eat meat, they must combine foods in a way that provides those essential amino acids.
C) Lentils and corn provide precursors to the eight essential amino acids, therefore when they are eaten together the body can produce the essential amino acids.
D) Eating meat only provides some of the essential amino acids, therefore it is fine that vegetarians don't eat meat.