Ecotourism can be defined as responsible travel to natural areas that aims to both conserve the environment and bring economic opportunities to local people. Ecotourism provides an alternative to environmentally damaging industries such as logging and mining, while also stimulating the local economy. However, its dependency on foreign investment leads to one of the main criticisms of the industry: that the profits generated from ecotourism do not benefit the local economy and work force. Furthermore, while the ideals behind ecotourism are unobjectionable, the industry is highly susceptible to greenwashing  whereby a false impression of environmental friendliness is given. More radical opposition comes from those critics who believe that ecotourism is inherently flawed because travel that uses fossil fuels is damaging to the environment. Despite these voices of dissent, ecotourism has become the fastest-growing sector of the tourism industry, growing at an annual rate of twenty to thirty percent. Ironically, ecotourisms very success may counteract its environmental goals, as high levels of visitors  even careful ones  inevitably damage the ecosystem.

Question: Ecotourisms critics believe that air travel contributes to global warming.
Options:
A. true, B. false, C. uncertain
Answer: "C"