In a CART decision tree algorithm, consider Gini impurity as the splitting criterion. A split S divides the records at the parent node into two pure leaf nodes as the two sub$-$trees. What is the Gini impurity of split S$?$

a$)1$

b$)0$

C$)$ We need to know the number of records in each sub$-$tree, and the data record distribution in each sub$-$tree to compute

d$)$ We need to know the number of records in each sub$-$tree to compute.