How do I change the setting so that all-in-capital words are recognized as a Multiterm term instead of untranslatable variables?

Dear Studio 2015 users,

I am working on a project for which I created a termbase from the client's glossary.  I have noticed that termbase terms that are made by all capital letters are not recognized by Termbase.  For example, AC is a term from this termbase.  When AC appears in a segment, AC does not show up in the termbase recognition window.  

It seems AC is being recognized as a variable (it has a underline).  How can I change the project setting so that AC would be recognized as a Multiterm term instead of a variable?

Thank you so much for your help.

Chunyi