单选题 Pr0l0nged e0nta0t between an irreversible hydmc0li0id impressi0n material and gypsum sh0uld be av0ided because（ ）。 A、the gypsum will sh0w 1-drge cracks B、a sOft，chalky surface can f0rm 0n the gypsum C、disc0l0rati0n Of the gypsum will 0cL1u