endangered species/ protect and save/ future generations/ experience/ their presence and value/

• A. 
  Endangered species should be protected and saved; therefore, future generations can experience their presence and value.
• B. 
  Endangered species could be protected and saved; as a result, future generations can experience their presence and value.
• C. 
  Endangered species have to be protected and saved since future generations can experience their presence and value.
• D. 
  Endangered species must be protected and saved so that future generations can experience their presence and value.