The diagram above suggests that a. the earth has not changed over geologic time. b. geologic time periods occur in repeating cycles. c. the earth has changed over geologic time. d. geologic eras occur in repeating cycles.

It has the highest concentration of hydroxide ions.

Explanation:

1) The pH is the measure of the acidity of a solution

2) pH is the logarithm of the inverse of the concentration of hydronium ions.

The higher the concentration of hydronium ions the lower the pH. A low pH indicates a high acidity. A high pH indicates a low acidity.

So, a more concentrated acid is more acid and its pH is lower.

3) The basicity is calculated using the concentration of hydroxide ions. The pOH is the measure of basiciy.

4) pOH is the logarithm of the inverse of the concentration of hydroxide ions.

5) The higher the concentration of hydroxide the lower the pOH and the more basic the solution.

This is, a more concentrated base will be more basic.

So, the only answer possible is that solution IV is considered the most concentrated base out of the four substances because It has the highest concentration of hydroxide ions.