A \( \mathrm{Ca}\left(\mathrm{H}_{2} \mathrm{PO}_{4}\right)_{2} \)
B \( \mathrm{Ca}\left(\mathrm{H}_{2} \mathrm{PO}_{4}\right)_{2} \cdot \mathrm{H}_{2} \mathrm{O} \)
C \( \left(\mathrm{NH}_{4}\right)_{2} \mathrm{HPO}_{4} \)
D \( \left[2\left(\mathrm{CaSO}_{4} 2 \mathrm{H}_{2} \mathrm{O}\right)\right] \)