X-ray examination of a recently discovered painting -- judged by some authorities to be a self-portrait by Vincent van Gogh -- revealed an underimage of a woman' s face. Either van Gogh or another painter covered the first painting with the portrait now seen on the surface of the canvas. Because the face of the woman in the underimage also appears on canvases van Gogh is known to have painted, the surface painting must be an authentic self-portrait by van Gogh. The conclusion above is properly drawn if which of the following is assumed? ['A painted canvas cannot be reliably attributed to an artist unless the authenticity of any underimage that painting might contain can be reliably attributed to the artist.', 'If a canvas already bears a painted image produced by an artist. a second artist who uses the canvas to produce a new painting tends to be influenced by the style of the first artist.', 'Many painted canvases that can be reliably attributed to van Gogh contain underimages of subjects that appear on at least one other canvas that van Gogh is known to have painted.', 'Any painted canvas incorrectly attributed to van Gogh would not contain an underimage of a subject that appears in authentic paintings by that artist.']