Which of the following is not a feature of the contingent valuation method?

Contingent valuation elicits stated willingness to pay or accept for a specified hypothetical nonmarket change. It applies to water quality, ecosystems, biodiversity and many other goods, not only air pollution. Nonmarket valuation and missing-market contexts are consistent with its use. It is an economic non-market based valuation method It is based on the maximum willingness to pay by the consumers It is used only in case of air pollution It is used under the condition of market failure