If xxx is a real number and y=12(ex−e−x)y=\frac12(e^x-e^{-x})y=21(ex−e−x), then Axxx can be either log(y+y2+1)\log(y+\sqrt{y^2+1})log(y+y2+1) or log(y−y2+1)\log(y-\sqrt{y^2+1})log(y−y2+1)Bxxx can only be log(y+y2+1)\log(y+\sqrt{y^2+1})log(y+y2+1)Cxxx can be either log(y+y2−1)\log(y+\sqrt{y^2-1})log(y+y2−1) or log(y−y2−1)\log(y-\sqrt{y^2-1})log(y−y2−1)Dxxx can only be log(y+y2−1)\log(y+\sqrt{y^2-1})log(y+y2−1)