Answer: D
A catalyst is a substance that alters the reaction and doesn't involve in the reaction.So if the Manganese was a catalyst the mass would not have decreased,it would just continue aletring the reaction until its used up.
The Manganese is not acting as a catalyst
D, is the final answer... others are simply not plausible
The Cold War was a state of geopolitical tension after World War II between powers in the Eastern Bloc and powers in the Western Bloc. Historians do not fully agree on the dates, but a common timeframe is the period between 1947, the year the Truman Doctrine was announced, and 1991, the year the Soviet Union collapsed. If you want to make sure this is the right answer for to the link below hope this helps on what ur looking for.http://www.history.com/topics/cold-war/cold-war-history
