One important contribution of the World Tourism Organization is

One important contribution of the World Tourism Organization is ______, which includes studying the features of international tourism.
A、research
B、design
C、marketing
D、statistics
【正确答案】：A
【题目解析】：选项A，“research”意为“研究”。根据题干中的“which includes studying the features of international tourism”，即“包括研究国际旅游的特点”，可以推断出这个空格应该填入的词与“研究”相关。因此，“research”符合语境，A选项正确。