Janine set up an experiment to compare the amount of carbon dioxide produced by water plants. She used identical glass jars, M, N and O. Each jar contained the same amount and type of water plants and was filled with 500ml of water. An equal amount of liquid X was added to each jar of water. Only Jar O was coated with black paint as shown in the diagram below.
All the set-ups were placed near a window on a sunny day from 9 am to 5 pm.
The colour of water with liquid X will change when exposed to a different amount of carbon dioxide as shown below.
|Amount of carbon dioxide||higher than normal||normal||less than normal|
|Colour of water with liquid X||yellow||red||purple|
Which of the following shows Janine’s observation of the colour of water with liquid X correctly at the end of the experiment?