题目

How do you define diplomacy（外交）? For the group Physicians for Peace（PEP），diplomacy is all about taking medical education and care to places where they are needed most．PEP brings together medical volunteers from different cultures and opposing sides of conflicts．Its message is “bring peace and international friendships through medicine”． PEP is based in the American state of Virginia．Doctor Charles Horton，a plastic surgeon（整形外科医生）known for his humanitarian work，established the group in the 1980s． More than 500 teams of doctors，dentists，nurses We can have_______ bluer sky if we create________ less polluted world． A．a；a               B．a；the                C．the；a              D．the；the