johns biology class was studying curious ways to recycle materials,including the use of compost as fertilizer.members of dance class investigated the effectiveness of various recycled materials in promoting plant growth.jon and three members of his lab group decided to compare the effect of compost and commercial fertilizer on plant growth.three plots have been plants(25 plants per plot)we're grown for five days.the plants were then fertilized as follows: Plot A received 10 g of commercial fertilizer; Plot B received 10 g of ageed compost;and Plot C receives no fertilizer.the plants receive the same amount of sunlight and water each day.at the end of 20 days the students recorded the height of the plants in cm.


1.) which plot is a control group ?

2.) what is the change variable ? ​