Schedule K-1: when were assets aquired?

I rec'd a Schedule K-1 (1041) with a long term cap gain.  This was a one time trust distribution from the sale of a family business.  This $ would have gone to my father, but came to me, as my father is deceased.

TT is asking me what portion of the assets were acquired before Dec 30, 2011.  Not sure how to answer this!  Acquired by whom, exactly?  How would I possibly know?  This is not a business I was involved in.