challenge: What is the mainstream scientific opinion regarding the Azuara impact structure?
  
  A. It is considered to have impact breccias and dike breccias as karst features
  B. It is interpreted as having shock metamorphism according to Langenhorst & Deutsch 1996
  C. It is believed to have Quaternary alluvial fans as impact ejecta
  D. It is confirmed to be of impact origin with shock effects
  Answer: 