challenge: What was the outcome of a 2020 study on the classification of species in the genus Ophichthys?
  
  A. They were merged with the genus Synbranchus
  B. They were determined to be a type of fish that does not exist
  C. They were found to be a subset of the genus Anguilla
  D. They were reclassified as a distinct monophyletic clade from Monopterus
  Answer: 