[A] If the item does not have a category, it will show undefined in the product category pie chart in the BI module.
[B] This will prevent you from making a meaningful analysis. Hence it is important that a category should always be defined for the product or item.
[C] In case you wish to add Item category now, you can simply add the item category. To add an item category, follow the steps given in the below link:
Keywords: Undefined, Product Category, Pie Chart