Why is the kappa lower for question 7 (decision tree with cross-validation) than question 4 (decision tree with no cross-validation)?

Select one:
A. K-fold-cross-validation is not as good as leave-out-one cross validation
B. You shouldn't use kappa with k-fold-cross-validation
C. Using cross-validation overfits to the training sample
D. Not using cross-validation overfits to the training sample