choose the molecule that is most concentrated at each ph.\nph = 4\nph = 7\nph = 10

Explanation:

Step1: Check pH = 4

At pH = 4, observe the graph. The red - colored curve representing $H_2CO_3$ is at the highest position among the three curves, meaning $H_2CO_3$ has the highest concentration.

Step2: Check pH = 7

At pH = 7, the blue - colored curve representing $HCO_3^-$ is at the highest position among the three curves, so $HCO_3^-$ has the highest concentration.

Step3: Check pH = 10

At pH = 10, the dark - blue colored curve representing $CO_3^{2 - }$ is at the highest position among the three curves, so $CO_3^{2 - }$ has the highest concentration.

Answer:

pH = 4: $H_2CO_3$ pH = 7: $HCO_3^-$ pH = 10: $CO_3^{2 - }$