Geologists recently discovered marks that closely resemble worm tracks in a piece of sandstone. These marks were made more than half a billion years earlier than the earliest known traces of multicellular animal life. Ttherefore, the marks are probably the traces of geological processes rather than of worms. Which one of the following, if true, most weakens the argument? ['At the place where the sandstone was found, the only geological processes that are likely to mark sandstone in ways that resemble worm tracks could not have occurred at the time the marks were made.', 'There were some early life forms other than worms that are known to have left marks that are hard to distinguish from those found in the piece of sandstone.', 'Most scientists knowledgeable about early animal life believe that worms are likely to have been among the earliest forms of multicellular animal life on Earth, but evidence of their earliest existence is scarce because they are composed solely of soft tissue.', 'It is sometimes difficult to estimate the precise age of a piece of sandstone.']