The diagrams that shows the repeating groups of atoms that make up the samples which were mixed together is option D.
A chemical reaction is said to have occurred when there a rearrangement of atoms in a substance. This rearrangement of atoms in the substance leads to the formation of new substances.
In this case, we must note that the combination of reactants to be chosen must posses the atoms shown as part of the one of the end substance. The only option that satisfies this requirement is option D.
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