challenge: What is the typical height of the Phacelia nashiana stem?
  
  A. Up to 2 metres (6.6 ft) tall
  B. Up to 1 metre (3.3 ft) tall
  C. Up to 8 centimetres (3.1 in) tall
  D. Up to 50 centimetres (19.7 in) tall
  Answer: 