Answer is: a) is has increased.
There are two types of reaction:
1) endothermic reaction (chemical reaction that absorbs more energy than it releases).
For example, the breakdown of ozone is an endothermic process. Ozone has lower energy than molecular oxygen (O₂) and oxygen atom, so ozone need energy to break bond between oxygen atoms.
2) exothermic reaction (chemical reaction that releases more energy than it absorbs).
For example, ΔH(reaction) = -225 kJ/mol; this is exothermic reaction.
