Which is the control group in the experiment? A. Pillar coral in their shallow water habitat, where the water has
experienced little change in temperature in 20 years
B. Pillar coral in their shallow water habitat, where the water has warmed
over the last 20 years, encouraging the growth of organisms that block
light from reaching the zooxanthellae

1) The process arrow A represents is photosynthesis.

2) Arrow A represents light energy transformation. Light energy from the sun is converted into chemical energy in plants.

3) Photosynthesis is part of a carbon recycling process in the carbon cycle. Plants absorb light energy and convert it to chemical energy. Plants absorb carbon dioxide which is exhaled by humans and animals. Plants then produce oxygen which is absorbed by humans and animals. Animals also eat plants thus passing the carbon compounds along.

I hope this makes sense. Hope this helps! :)