In which sentence is the action arrow pointing in the correct direction?
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leslie left the house early but had to go back when she forgot her books.
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leslie left the house early but had to go back when she forgot her books

I would say the first answer is correct, because she first left the house, but then had to go back because she forgot her books.
The actions are linear - we have one action that happened first, and was followed by another later action.

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