Carbon atom with iron and helium
Explanation:
The reaction between calcium hydroxide and nitric acid is as follows.

Number of reactant atoms are as follows.
Number of product atoms are as follows.
To balance the given chemical equation, multiply
by 2 on reactant side and multiply
by 2 on the product side.
Therefore, the balanced chemical equation will be as follows.

A drop of iquid mercury is D. <span> a pure substance and an element. This is because mercury is an element which exists as liquid in the normal or standard conditions. It is a metal that is toxic to all environments. It is pure because it is composed only of one kind of substance.</span>