Which of the following most accurately describes the parameters of a generalized Pareto distribution (GPD)?
　　A. β The scale parameter: 0 > β. The shape (tail) index: ξ, can be any real number.
　　B. The scale parameter: β, can be any real number. The shape (tail) index: ξ, can be any real number.
　　C. The scale parameter: 0 < β. The shape (tail) index: ξ, can be any real number.
　　D. The scale parameter: β, which can be any real number. The shape (tail) index: ξ > 0.
　　Answer:C
　　The two parameters are a scale parameter, which must be positive, and a shape parameter that can take on any value.