I dont want to mislead you, but I believe the answer is A because letter B is wrong because plants go through cellular respiration and photosynthesis, whereas animals go through cellular respiration but not photosynthesis, and for C, I've never heard of that so it doesnt seem likely.
I guess because of concentration.....it stops !
If a fabric has been tested for pilling, the grade can be located on the fabric sample and online. ISO-12945-2: 2000 Martindale Method with 415g loading mass