Hi Michael,
You have to load the iris dataset and then go to Classify. In Classify, select ZeroR as your Classifier and make sure the cross-validation is selected. You have to perform 6 operations with different number of folds (10 to 15)
Each operation will give you a result in the Result list (lower left box). The value you should look after is the "Correctly Classified Instances" percentage. If Weka gives you 4 digits of precision, you have to mentally do the rounding to the nearest integer value. Look for the minimum and maximum values and you get the answer.
Good luck!
Gabriel Santos
Macau
Community TA