Alanine and Lysine Are Both Amino Acids

Alanine and lysine are both amino acids. Not eating enough lysine can lead to protein deficiency, whereas not eating enough alanine does not lead to protein deficiency. Why is this the case?

A) Alanine can be synthesized by cellular biochemical pathways, whereas lysine cannot.
B) Alanine can be easily replaced by other amino acids in protein synthesis, whereas lysine cannot.
C) Lysine is needed in much larger quantities for protein synthesis than alanine.
D) The body has a more difficult time absorbing lysine than alanine, so more must be consumed to avoid protein deficiencies.
E) All of these choices are correct.