How is it possible that one or more of the training instances used to build a decision tree may not be

classified correctly by the tree?

a$.$ Two instances exist in the data with identical values for all input attributes but differing values for

the output attribute.

b$.$ The predefined criteria for terminating one path of the decision tree is met and one or several

instance from at least two classes follows the path.

c$.$ The same categorical attribute is selected for more than one node in the decision tree.

d$.$ More than one of a$,$b$,$ or c is correct.