The correct answer is option D, that is, exactly 0.3 Kg.
This is due to the fact that at the time of a physical change, like getting dissociated into fragments or parts, mass is conserved. In the given case, the glass cup exhibited a mass of 0.3 Kg prior of getting dissociated, so in case, if Regan gathered all the dissociated parts, they would possess a mass of exactly 0.3 Kg in combination.