What is another name for the Cotton Mouth Snake?

The Cotton Mouth Snake is indeed commonly referred to as the Eastern Cottonmouth. This name reflects its geographical range, as it is most prevalent in the eastern regions of the United States. Known for its distinctive behavior of "playing dead" and its characteristic open-mouth display when threatened, the Eastern Cottonmouth is a venomous pit viper that is often found near water bodies.

The other choices represent different species or scientific terms relevant to other snakes. For example, the scientific name Agkistrodon piscivorus is accurate for describing the Cottonmouth’s broader classification but does not serve as an alternative common name. Similarly, the Carolina Pygmy Rattlesnake and Sistrurus miliarius barbouri refer to entirely different species, which do not share the common name or traits associated with the Cotton Mouth. Therefore, the most fitting and recognized alternative name for the Cotton Mouth Snake within the context of its common usage is indeed the Eastern Cottonmouth.