C-09-Q009mediumsingle_mcqCaO+2HCl→X+H2O\mathrm{CaO + 2HCl \rightarrow X + H_2O}CaO+2HCl→X+H2O. Here X is—aCaCl\mathrm{CaCl}CaClbCaCl2\mathrm{CaCl_2}CaCl2c