The correct option is
C CaOConcentrated
H2SO4, anhydrous
CaCl2 and
P4O10 are not used to dry ammonia because
NH3 is basic and will react with them.
NH3+Conc.H2SO4→(NH4)2SO4 NH3+P4O10→(NH4)3PO4
NH3+CaCl2→CaCl2.8NH3 The gas is passed through fresh quicklime (solid CaO lumps) to effectively dry it.