Conservators disagree about why fine networks of cracks continue to appear in the glaze of some earthenware vessels long after the vessels leave the kiln. One account attributes the cracks almost entirely to stresses created as the glaze and clay body cool at different rates; another proposes that, after firing, the porous clay body gradually absorbs moisture and expands beneath the glaze. The accounts imply different effects of storage conditions. If moisture-driven expansion is an important cause, then identically fired pieces kept in humid air should develop more new cracks than pieces kept in dry air. Materials scientist Imani Cole tested newly made replicas, storing half in humid air and half in dry air. After eighteen months, the humid replicas had accumulated substantially more cracks, although all the replicas had undergone the same firing and cooling process. Cole cautions that initial cooling stress may still explain some cracks but argues that moisture can drive later crack growth.
Which choice best describes how the underlined sentence contributes to the text’s discussion?