The answer would be A: its container.
Gas will expand to fill whatever container it is put in.
Is A have a nice day good luck b
Answer: solid
Explanation: Chemical reactions are those which involve rearrangement of atoms.
Chemical changes are accompanied by following changes:
1) Absorption or release of heat
2) Change in color
3) Formation of gas bubbles
4) Formation of a solid product called as precipitate
Example of formation of precipitate or solid in chemical reaction:
Sodium reacts with water to form a colorless solution of sodium hydroxide and hydrogen gas.