During a physical science lab investigating chemical reactions, several students placed a 30g antacid tablet in a 30g zip-lock bag. They recorded the masses of the tablet, and the bag. Then they added 50 grams of water and quickly sealed the bag. The tablet began to fizz and soon disappeared. The bag was filled with gas. If the mass of the liquid after the reaction is completed is still 50 grams, how much gas is produced? A) 30 grams B) 50 grams C) 80 grams D) 90 grams