To determine whether prehistoric potters deliberately added shell to clay, archaeologists at one river-valley site compared vessel fragments with nearby raw clay. The vessels contained sharply broken shell distributed evenly, a pattern researchers also produced by intentionally crushing and kneading shell into clay; raw clay instead contained rounded shell scattered irregularly. These findings make deliberate addition a reasonable explanation for the vessels’ pattern. _____ those findings do not establish why the potters added the shell: the same preparation could have been intended to change the clay’s texture, reduce cracking, or serve some other purpose.
Which choice completes the text with the most logical transition?