The correct option is B False
Double salts are salts containing more than one cation or anion, and is obtained by combination of two different salts which were crystallized in the same regular ionic lattice. Examples of double salts
include alums,potassium sodium tartarate and potassium aluminum sulfate and has the chemical formula KAl(SO4)212H2O. Carnallite (KMgCl36H2O). Dolomite CaMg(CO3)2.Cerrusite (PbCO3) Cerrusite is not double salt.
Hence options A,B & C are correct.