One of the processes used for concentration of ores is Froth floatation process. This process is generally used for concentration of sulphide ores. Sometimes in this process we add NaCN as a depressant. NaCN is generally added in case of ZnS and PbS minerals. What is the purpose of addition of NaCN during the process of Froth floatation?

• A. NaCN causes reduction by precipitation
• B. A soluble complex is formed by reaction between NaCN and ZnS while PbS forms froth
• C. A soluble complex is formed by reaction between NaCN and PbS while ZnS forms froth
• D. A precipitate of \[Pb{{(CN)}_{2}}\] is produced while ZnS remain unaffected.