D. Lead nitrate
Explanation:
When 2 solutions of two different ionic compounds with a common ion comes into contact with each other, then the solubility of those ionic substances reduces significantly. For instance, when we try to dissolve solid sodium chloride (NaCl) in a solution of the chloride ions (Cl⁻), we can see that the quantity of NaCl that might dissolve to attain the saturation point could be lowered. This occurrence is called as common ion effect also it plays an important roles in environmental as well as in pharmaceutical areas.
Addition of lead nitrate which has Pb²⁺ ion to the saturated solution of PbCrO₄, leads to the common ion effect due to the presence of Pb²⁺ ion as the common ion.
