When a solution is allowed to crystallize slowly, impurities are excluded from the growing crystal structure because: A. The molecules in the crystal lattice are cooler than the solvent and impurities would have too high a melting point to join the lattice. B. The molecules in the crystal lattice are in equilibrium with the molecules in solution and molecules that don't fit well into the lattice (impurities) are likely to return to the solution. C. Impurities could never join the lattice because they are always liquid at room temperature. D. During slow crystallization, impurities are prevented from joining the crystal structure because of their ionic strength.