Which amino acid from following contains - CH ₃ as side chain ?

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An amino acid's structure consists of a central alpha-carbon bonded to an amino group ( - NH ₂ ), a carboxyl group ( - COOH ), a hydrogen atom ( - H ), and a side chain (R-group) that defines the amino acid's identity. Analysis of the R-groups: Leucine (A): - – CH ₂ CH ( CH ₃)₂ Alanine (B): - – CH ₃ Serine (C): - – CH ₂ OH Valine (D): - – CH ( CH ₃)₂ The methyl group ( - CH ₃ ) appears as the R-group in alanine.