Read the following passage and mark the letter A, B, C, or D to indicate the correct answer to each of the questions.

One of the biggest issues that eco lodges and green hotels face is the lack of a universal definition. How eco-friendly does a lodge or boutique hotel need to be to qualify? And who determines which accommodations will pass muster?

Unfortunately, some of the world's most well-known and respected "green" certification programs are cost-prohibitive for many eco lodges, which are often relatively small and owned and operated by independent entrepreneurs rather than corporations.

But there are numerous reputable certification programs that responsible travelers can look for before they book an eco lodge or hotel stay. Many - including Green Seal in the U.S. - are part of the Global Ecolabelling Network, a non-profit group comprised of 25 third - party organizations throughout the world. They are all devoted to improving, promoting and developing labelling systems for eco-friendly products and services.

Arctic Tundra Lodge in Churchill, Manitoba Sponsored in part by the United Nations World Tourism Organization, the Global Sustainable Tourism Council (GSTC) Criteria are widely considered the gold standard in “green” certification. These criteria involve effective sustainability planning, maximizing social and economic benefits for the local community, enhancing cultural heritage, and reducing negative impacts on the environment.

Where the GSTC has guidelines for destinations, hotels and tour operators, Green Key Global is designed specifically for the lodging industry. Its flagship Eco-Rating Program, which evaluates properties on an environmental, social and economic level, has certified around 2,370 green hotels and eco lodges in 52 countries over the past 15 years.

Green Globe is another popular certification program, offering training and education for hotels/resorts, attractions, organizations, cruise ships, and various tourism industry suppliers. Their global network of independent auditors provides third-party inspection and an internationally recognized seal of approval that's become increasingly popular over the past 25 years.

The passage mainly discusses ____.