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Answer</h2>
It will be single step endothermic reaction.
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Expalantion</h2>
In the endothermic reaction, the reactants come together to convert to products by absorbing the heat from the external source. This reaction is explained is also known as one step reaction as reactants meet to get the transition stage and converts to the product. But in some reactions, the activation energy required to activate the reactants to get the transition stage to form products. For this, the reaction will have the steps as activation energy, reactant meet, transition stage and products form.
An important aspect of fission reactions is that they produce free neutrons, which causes chain reactions.
The phrase "light year" is a <u><em>distance</em></u> ... it's the distance that light travels through vacuum in one year.
When you look at an object located 1 light year away from you, you see it as it was 1 year ago.
If a star located 10 light years away from us suddenly brightens, or dims, or explodes, we see the event <em>10 years later.</em>