Allow selection of only one option in field list

Is it possible to allow only one option to be selected in a field list?

Here is a link to the section of my website where I am using JL Content Field Filter
fairway-is.eu/index.php/farm-management/management-tools/d5-4

For example, there are 3 countries in the Country list.
If Ireland is selected, there are no results returned (correct).
If Denmark is selected, the article ISIP is returned (correct)
However if both Ireland and Denmark are selected the article ISIP is returned (incorrect because ISIP is only in the Denmark field).

The problem would be solved if only one selection was allowed per field. Is it possible to do this?

Many thanks for all your help.

Jane

I'm sorry, I've found the solution. I needed to edit the fields and change the field filtering parameters to "radio".

Thank you again for your excellent extension.