One of the main of the summit was “sustainable development”,or the question how we can continue developing the world without damaging the environment.
A. headlines
B. themes
C. topics
D. deadlines
网友回答
A. headlines
(答案→)B. themes
C. topics
D. deadlines
解析：headline大字标题；theme主题,主旋律；topic话题,主题；deadline期限。这里指的是大会的主题,应用theme。