O-LevelBiologyPlant Nutrition5090/11 · May/June 2013 · Q71 Mark
A green leaf is picked at time 07.00 and immediately placed in a sealed test-tube containing hydrogen carbonate indicator solution. The tube is kept near a window for 24 hours. The table shows how the indicator changes in colour. [Figure showing a test-tube with a leaf in hydrogen carbonate indicator solution.] [Table showing 'colour' and 'amount of carbon dioxide compared to average atmospheric concentration': purple for less than normal, red for normal, yellow for more than normal.] Which colour will the hydrogen carbonate indicator be at times 12.00 and 24.00?
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Aat 12.00: purple, at 24.00: yellow
Bat 12.00: red, at 24.00: purple
Cat 12.00: yellow, at 24.00: purple
Dat 12.00: yellow, at 24.00: red
✓ Correct answer
A: at 12.00: purple, at 24.00: yellow
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