A learner carried out an investigation into diffusion. A piece of agar measuring $1.0\,\text{cm} \times 1.0\,\text{cm} \times 1.0\,\text{cm}$ was evenly coloured with a water-soluble blue dye. The agar block was placed in a test-tube with $10\,\text{cm}^3$ of distilled water at $20^\circ\text{C}$. After five minutes, the blue colour intensity of the water was measured. Four further experiments, A, B, C and D, were then done using different numbers of agar blocks, different agar block sizes and different temperatures. All the other variables were kept constant. Which experiment would produce a paler blue colour in the water after five minutes than the first experiment?
Biology 9700 · AS & A Level · Movement into and out of cells