Step 1: Concept
Classification of amino acids based on side-chain composition.
Step 2: Meaning
Some amino acids contain sulfur atoms in their R-groups.
Step 3: Analysis
Cysteine contains a thiol group ($-SH$), while Methionine (not listed) is the other common sulfur-containing amino acid.
Step 4: Conclusion
Hence, Cysteine is the correct answer.
Final Answer: (E)