Which Statement About Proteins and Amino Acids Is True

Which statement about proteins and amino acids is true?

A) Human infants require fewer essential amino acids than human adults do.
B) Individuals with phenylketonuria convert phenylalanine to tyrosine.
C) Proteins are completely broken down to their constituent amino acids before being used by the body.
D) Most essential amino acids are required at some times in life but not at others.
E) Rice and corn each have two essential amino acids not found in the other.