Answer & Explanation
A) Sheela is not happy and she goes to work.
The event of "Sheela is not going to work" happens only when the event "Sheela is happy" happens. Also, if the event "Sheela is happy" does not happen, then the event "Sheela is not going to work" will not happen. In other words, if it is true that Sheela is not happy, then it means that Sheela is going to work.