Students set up apparatus to measure the uptake of water by a leafy shoot. They recorded the position of the air bubble at the start. They observed the apparatus for 10 minutes, and recorded the distance travelled by the air bubble at one-minute intervals. They then switched on a fan pointed towards the leafy shoot and recorded the distance travelled by the air bubble from the start, each minute, for another 10 minutes. Which graph would they draw from their data?

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