Answer:
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The answer should be 1 AU as it’s just about close to the number of miles from earth to sun.
Earth to sun in miles is -92.96
1 AU is- 92955807.3
The complete chemical reaction of aqueous Sodium sulfate and aqueous Barium nitrate is

The right side and the left side of the reaction have equal number of elements, therefore it is balanced.
Activation energy is defined as the least amount of energy that is needed to be available in a chemical system with potential reactants in order to result a chemical reaction. Therefore, the correct answer would be the first option: the heat released in a reaction.