Correct Answer (Detailed Explanation is Below)
B.
Syn-propanethial-S-oxide
Detailed Explanation
Syn-propanethial-S-oxide is the lachrymatory factor responsible for onion-induced tears. Cutting onion damages its cells and allows enzymes to react with sulfur-containing compounds, ultimately producing this volatile compound. It irritates the eyes and stimulates tear production. Important related terms include
lachrymator, sulfur compounds, enzymes and volatile compounds.