A is the best answer, a visual aid would help most in this situation.
A human
crawls then walk then has a cane
Answer: Pythons are negatively affecting the local ecosystem.
Explanation:
Thousand of pythons are living in the Everglades, is just a fact.
Large rewards are being offered to capture and kill pythons, is also a statement. It's not a reason why pythons should be hunted, just a fact on what you'll get if you kill pythons. Of course... there is a reason why pythons should be hunted, but it is not stated here, so it's not the answer.
People who brought them here as pets created the problem. This isn't explaining the problem, just creating a scapegoat.
