En la boda de Elena en 2005, a tus padrinos no les los instrumentos en el baile.

gustaba
gustaban
gustabas
gustaron

gustaban

Explanation:

Because, gustaban ends in a -an, which means that it applies to the they/y'all because the subject is "your parents", being plural. And -an means that what it is talking about is plural.

answerestan corriendo; i believe this is correct, plz check first good luck;