The simple trick which one can consider in such problem where it is asked for positron emission is :
<span>When the atomic number goes DOWN by one and mass number remains unchanged, then a positron is emitted.
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<span>a. </span>

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Here the atomic number decreases by one.
Similarly, options b and d are eliminated.
Option c is also not the answer.
For c, Count the atomic number on left side and compare it with right side. You will see it is 9 on left and 8 on right. Atomic no. did go down by 1. But the atomic mass is changed as well.
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The unbalanced equation is one in which the moles of atoms are not equal on both sides of the reaction.
<h3>What is a balanced chemical equation?</h3>
A balanced chemical equation is one in wgich the moles of atoms in the reactants side is equal to the moles of atoms on the product side.
The given equations of reaction is not clearly stated.
Therefore, the unbalanced equation is one in which the moles of atoms are not equal on both sides of the reaction.
Learn more about balanced equations at: brainly.com/question/11904811
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Everything is made of atoms. An atom is the smallest particle of an element, like oxygen or hydrogen. Atoms join together to form molecules. A water molecule has three atoms: two hydrogen (H) atoms and one oxygen (O) atom.