Agar cubes can be used to demonstrate the effect on diffusion of changing the surface area to volume ratio. Three different agar cubes made using a coloured indicator solution were placed into a dilute acid that diffused into the cubes. As the acid diffused into the agar cubes, the colour of the indicator solution changed. The cubes had volumes of 1 cm³, 2 cm³ and 3 cm³ and were left in the dilute acid for 10 minutes. All other variables were kept the same. After 10 minutes, the agar cubes were removed from the dilute acid and cut in half. The cut surfaces were observed and the results were recorded as diagrams. All diagrams were drawn to the same scale. The results for the 2 cm³ cube are shown. [Figure 19.1] Which diagrams show the results for the 1 cm³ and the 3 cm³ cubes?

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