Final answer:
The amino acids containing a sulfur atom are cysteine and methionine, making 'B and C' the correct answer.
Step-by-step explanation:
The amino acids that contain a sulfur atom are cysteine and methionine. Cysteine has a sulfhydryl (SH) group in its side chain, and methionine has a thioether (CH3S) in its side chain. Tryptophan, on the other hand, does not contain sulfur. Therefore, the correct answer is option 5, 'B and C'.