I didn't stay behind because I wanted to, I did so because it was my ________.    work    duty    shift    chore

To fill in the blank in the sentence "I didn't stay behind because I wanted to, I did so because it was my ________," we need to consider the context of the statement. The options provided are “work,” “duty,” “shift,” and “chore.”

1. Work - This refers to tasks or efforts that one engages in, but it does not strongly convey a sense of obligation.
2. Duty - This implies a moral or legal obligation to perform a task, which fits the context of doing something not out of desire but obligation.
3. Shift - This generally refers to a scheduled period of work, which could apply but lacks the nuance of personal responsibility.
4. Chore - This implies a mundane task usually done at home, which does not quite match the tone of the statement.

Considering the nuances of each option, "duty" is the most appropriate choice as it conveys the sense of obligation to remain behind.

Final Answer

duty