Sarin is a deadly nerve gas that was outlawed by the Chemical Weapons Convention of 1993. However, it has been used at various times as a weapon of mass destruction by terrorists, including a 1995 attack in the Toyko metro and a 2013 attack by the Syrian government on rebel forces during the Syrian civil war. Sarin is an acid fluoride and ester of methyl phosphonic acid. The S-enantiomer is more active than the R enantiomer. Select the structures corresponding to the more active isomer: H3C ...O H3C H3C