Cut pieces of agar jelly containing starch indicator can be used to investigate the factors affecting diffusion rates in cells. Four pieces of agar jelly of different shapes and sizes were soaked in a beaker containing a high concentration of iodine solution. When iodine diffuses into the agar, the starch in the jelly turns blue-black. Which of the following pieces of agar jelly would be the first to turn entirely blue-black?
a cube with edges of 3 cm3\text{ cm}3 cm each
a cuboid with dimensions 2 cm×4 cm×5 cm2\text{ cm} \times 4\text{ cm} \times 5\text{ cm}2 cm×4 cm×5 cm
a sphere with diameter 3 cm3\text{ cm}3 cm
a cuboid with dimensions 1 cm×3 cm×6 cm1\text{ cm} \times 3\text{ cm} \times 6\text{ cm}1 cm×3 cm×6 cm
