challenge: According to Mehrtens (1987), what happens when Metlapilcoatlus snakes strike at their assailants?
  
  A. They strike with such force that they actually leave the ground
  B. They strike with moderate force, about half of their own body length
  C. They only threaten with an open-mouthed display, but do not strike
  D. They coil and remain still, playing dead
  Answer: 