Detailed Instructions: Given a sentence and two mentions from the text (arguments), indicate a phrase (a verb or noun phrase) that describes the relationship between the provided arguments.
Problem:Sentence: 'Some say the December birthstone is the Blue Topaz , probably because it became quite popular as a jewelry stone , and many people started viewing the Zircon as a synthetic , confusing it with the cubic zirconia .', Argument/Subject 1: 'blue topaz', Argument/Subject 2: 'december'
Solution:
be birthstone for