When showing Select Lists that only contain 1 item it is nicer to shown these as Disabled, so the user can see at once that there is no option to choose from.
Normally you can do this manually for each Select List item. But for items that have Select List queries that are dynamic, you will need a dynamic solution.
The Dynamic Action in this example sets all Select Lists on the page to Disabled (during Page Load) if they only contain 1 item, and adds some CSS.
Note: items that have the "disabled" attribute set, will not have their session state set when submitting the page! So you may need some hidden items, or a similar solution...