Which of the following statements are correct regarding amino acids ?
A. They are substituted methanes.
B. Serine is an aromatic amino acid.
C. Valine is a neutral amino acid.
D. Lysine is an acidic amino acid.
Choose the correct answer from the options given below :

Amino acids are organic compounds containing an amino group and an acidic group as substituents on the same carbon, i.e., the $\alpha$-carbon. Therefore, they are considered substituted methanes. Statement A is correct.

Serine contains a hydroxymethyl group ($\text{-CH}_2\text{OH}$) as its side chain and is an aliphatic amino acid, not an aromatic one. Aromatic amino acids include phenylalanine, tyrosine, and tryptophan. Statement B is incorrect.

Valine contains one amino group and one carboxyl group, making it a neutral amino acid. Statement C is correct.

Lysine contains two amino groups and one carboxyl group, making it a basic amino acid, not an acidic one. Acidic amino acids include aspartic acid and glutamic acid. Statement D is incorrect.

Thus, only statements A and C are correct.

Answer: A and C only