The correct answer is - physical geography.
The focus of the physical geography is on the physical features on our planet, be it bodies of water, landforms, or natural resources. The physical geography is interested in the shape of the natural physical features, as well as their structure, how did they become like that, the evolution trends, what was the cause for them to form, and how will it all look like in the future. It is a very wide geographic area of study, and it has lots of sub-disciplines as part of it, in order for every specific aspect of the nature to be properly examined and explained.
Answer:Botulinum toxin
Explanation: Scientists differ about the relative toxicities of substances, but they seem to agree that botulinum toxin, produced by anaerobic bacteria, is the most toxic substance known.