$\begin{array}{1 1} \text{(a) Two sulphide ores can be separated by adding water to the ore and pine oil to the gauge or by adding selective depressant}\\ \text{(b) Two sulphide ores can be separated by adding detergents to the ore and oil to the gauge or by adding selective depressant} \\ \text{(c) Two sulphide ores can be separated by adding pine oil to the ore and water to the gauge or by adding selective depressant} \\\text{(d) Two sulphide ores can be separated by adding pine oil to the ore and fatty acids to the gauge or by adding selective depressant} \end{array} $