When we create a Decision Tree, how is the best split determined at each node? 
O We split the data using the first independent variable and so on. 
O The first split is determined randomly and from then on we start choosing the best split. 
O We make at most 5 splits on the data using only one independent variable and choose the split that gives the highest Gini gain. 
O We make all possible splits on the data using the independent variables and choose the split that gives the highest Gini gain.