According to the time line of the events that occurred, The event that happened second is that Barton works on the frontline of the civil war. That is option C.
What is a timeline of events?
The timeline of events are those events that occurred at a given time following a particular chronological line.
From the timeline of events given concerning Clara Barton, She worked as a federal patient clerk before working at the frontline of the civil war.
The word that is used to indicate the chronology of events in Barton's life is 'After'. This is because the events indicates the past life of Clara Barton.
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