C
Decomposition is of this form: A becomes B+C ... so after the reaction, the element A DECOMPOSES into two smaller elements, B and C.
Synthesis is the opposite: B+C becomes A AFTER THE REACTION.
Hope that helps :))
Answer: B is a gas because its volume is less than the volume of the containers.
Explanation: hope this help bye
The answer is gonna be the last one :)