The box below to the left represents ions in a certain volume of 0.10MHCl(aq) . In the box below to the right, draw a representation of ions in the same volume of 0.20MHCl(aq) . (Do not include any water molecules in your drawing.)

Explanation:

The first diagram shows the diagram to the question and the next which is the second diagram answers it.

We are told that the box on the left in the diagram contains certain volume of 0.10MHCl(aq)

Now if the volume is increased  to 0.20MHCl(aq) , the concentration too is increased and the particles in the left diagram is doubled which is shown in the right path of the diagram.

So from the left part , we have 4H⁺ and 4Cl⁻ ; when it is being doubled ; we have 8H⁺ and 8Cl⁻ as shown in the second part of the diagram.

the answer is definitely c.