<prompt> Free SH group is present inCysteineMethionineTaurineHomoserine  <response>: This is a tricky question. Option a, b and c have sulphur. But, only cysteine contains SH group. EXTRA EDGE:- Sulphur containing amino acids: Cysteine Methionine Homocysteine Taurine Sulfhydrylthiol group-containing amino acids: Cysteine Homocysteine Sulfhydrylthiol group-containing proteinogenic amino acids: Cysteine 