challenge: What is the typical depth range at which Synagrops japonicus can be found?
  
  A. 1,000-2,000 m (3,300-6,600 ft)
  B. 10-50 m (33-164 ft)
  C. 2,000-3,000 m (6,600-9,800 ft)
  D. 100-800 m (330-2600 ft)
  Answer: 