<span>A substance is composed entirely of one type of atom, it is known as a Chemical element
because mixture contain more than one type of atom and it cannot be neutron or isotope
so correct option is B
hope it helps</span>
<u>Explanation:</u>
A balanced chemical equation is one where all the individual atoms are equal on both sides of the reaction. It follows the law of conservation of mass.
When potassium phosphate reacts with silver nitrate, it leads to the formation of silver phosphate and potassium nitrate.
The balanced chemical equation follows:

When barium bicarbonate reacts with calcium hydroxide, it leads to the formation of barium carbonate, calcium carbonate and water
The balanced chemical equation follows:

Professor of Physics Carlo Rubbia