Please help.

I have a database with customer name at Column A, and the things they
purchased located from Column B, C, onward. They are 15 Fields, that customer
can buy.
Col B: Food
Col C: Drink
Col D: Food
Col E: N/A (the customer dont buy this item).
....
Col ?: Tool

how to know, that a customer buy only with one Category or more than two
category. But please be informed, if Customer A, buy Col B and Col D, i would
like still to consider that she buy one category of FOOD.

TIA.