A、It is $3.5 trillion. B、It is $30.5 trillion. C、It is $35 trillion. D、It is $350 trillion. C根据原文第一句中所提供的数字，进行简单运算推断，可知选项c的说法是正确

Global tourism is a $3.5 trillion industry that represents 10 percent of world GDP and employs more than 200 million people. Despite its global reach, tourism remains extremely fragmented; major hotel chains and tour operators represent only 20 percent of the business. Most companies—and countries—prefer to go it alone, even when it might be in their best interest to share data and marketing strategies. Now that’s changing. In the past year, Spain and Tunisia organized a conference to support Mediterranean tourism. Australia, New Zealand and Fiji have also come together for a joint marketing campaign. Luxury hotel associations, like Relais & Chateaux and Leading Hotels of the World, are exchanging customer information with high-end cruise lines and tour operators such as Abercrombie & Kent in an effort to jump-start business.