While configuring an item to add it to order, we could not remove the "none" radio button

In order creation page, after we click to the configure and add button, features and options of our item's structure appears. But for some options, even though mutually exclusive checkbox is checked in the item structure page, we still see the "None" radio button. We want user to select at least one option from that section. So how can we remove that none radio button from the options that is mutually exclusive?