Answer:
a. Glucagon is released by the beta cells of the pancreatic islets of Langerhans.
Explanation:
When the body is fasting, the pancreas releases glucagon so that your body can produce glucose. Glucagon is a protein hormone made and secreted by alpha cells from pancreatic islets (or islets of Langerhans).
The islets of Langerhans are a special group of cells in the pancreas that produce not only glucagon, but also insulin. These substances act as important regulators of sugar metabolism.
Explanation:
As far as I can think of, we're dependent on other species. If we can't be carnivores, then literally, the only other option I can think of is being a herbivore, and that still an organism. We need sufficient life essence to keep living. We CANNOT live without harming another organism.
In short of my babbling, human survival is not independent of other species.