This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
Cereals are deficient in: 
Select and explain. 
A. Tryptophan, B. Threonine, C. Lysine, D. Methionine
C: Lysine
Answer: C: Lysine 
Explanation: Lysine