$4.$ Which of the following is a common ion exchanger used in demineralization processes?a$)$ Calcium sulfateb$)$ Sodium carbonatec$)$ Zeolited$)$ Activated carbonWhat is the purpose of regenerating ion exchange resins in demineralization processes?a$)$ To remove suspended solidsb$)$ To restore their ion exchange capacityc$)$ To reduce pHd$)$ To enhance taste and odorWhat is the primary function of a deaerator in a boiler feed water system?a$)$ To remove dissolved gasesb$)$ To increase the temperature of waterc$)$ To add minerals to waterd$)$ To regulate the pressure inside the boilerWhich of the following is a common method for reducing dissolved oxygen in boiler feed water?a$)$ Adding oxygen scavengersb$)$ Increasing the temperaturec$)$ Decreasing the pressured$)$ Adding disinfectants