The importance of tourism to a country's economy can be measured

The importance of tourism to a country's economy can be measured by looking at the ______ of national income created by tourism.
A、overall
B、proportion
C、total
D、extra part
【正确答案】：B
【题目解析】：选项B，“proportion”的意思是“比例”或“部分”，它指的是某个事物在整体中所占的份额或比重。在这个语境中，使用“proportion”可以准确地描述旅游业创造的国民收入在整个国民收入中所占的比例，从而衡量旅游业对国家经济的重要性，所以B选项正确。