I think the correct answer is A
People who use complex tools like plows, irrigation, and fertilizers to grow domesticated plants are called farmers, it is a large scale activity and it´s use to obtain food from the earth, we also have horticulture, does not require hundreds or thousands of acres of land, horticulture is also important, but is more limited to the domestic and individual context, and finally it is much cheaper because it is not done at large scales like the Agriculture.
Yes, it is a weak acid called the citric acid
When the bird is decomposed, more energy is transfered since its's bigger than a fly, a spider and the amount of fruit a fly can eat.
Hope it helped,
BioTeacher101