A dataset contains $100$ instances. We use $10-$fold cross validation to partition the dataset to training$/$testing sets.

The accuracies for the ten experiments are $80\%,85\%,95\%,80\%,90\%,90\%,95\%,80\%,85\%,95\%$

What is the Cross$-$Validation$-$Accuracy?

a$.$

$95\%$

b$.$

$80\%$

c$.$

$85\%$

d$.$

$87\mathrm{.}5\%$