How to tell which one is a subsequent event for a company?

6. A subsequent event for an entity with a December 31, 2018, year-end would NOT include: A. A change in the estimated useful lives of equipment in January 2019. B.An issuance of bonds in January 2019. C. An acquisition of another company in January 2019. D. A major uncertainty at December 31, resolved in January 2019