challenge: In which regions of Portugal is Silene longicilia commonly found?
  
  A. Algarve and Costa Vicentina
  B. Douro Valley and Trás-os-Montes
  C. Serras de Aire e Candeeiros, Serra de Montejunto, Serra De Sintra, and Serra da Arrábida
  D. Serras de Aire e Candeeiros and Serra da Estrela
  Answer: 