Answer:
I am not completely sure about these answers, but I hope this will help a bit :) the independent group is the type of soil being used (as that is the one being manipulated by us), the dependent variable is the size of the pumpkin (as the size will depend based on the soil), the control group is the species of pumpkin seed (I'm not very sure about that though), and the constants are the type of pumpkin seed, the amount of water and the amount of sunlight. And lastly, I believe it is 3 trials for each soil. Sorry if I end up being wrong but I hope this helps a bit.