The reaction which is a self-sustaining series of chemical reactions in which the products of one reaction are the reactants in the next reaction is chain reactions.
What are reactants and products?
Reactants are those species which are present at the initial state of the reaction and at the end of the reaction we obtain products.
If in any chemical reactions, reactants are combined for the formation of products and for the further process obtained product will act as reactant and that chemical reactions are known as chain reactions. Because this process continues for long time.
Hence correct option is chain reactions.
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