I'd need more information on the wording of the question before saying too much on that one. After the head has cleared and you can remember more details let me know. I'm intrigued as to how they would put a question that expected you to use the ASDA instead of the TORA as the starting point for measuring the obstacle free distance. After all, the obstacle free path is relevant to a successful take-off and the TORA is important there. The ASDA is TORA plus stopway but the stopway is unuseable unless you're aborting the take-off. Then it becomes available for rollout while stopping.
... had a q that asked the exact length of the obstacle free path that I think involved using the ASDA instead of the TORA as the starting point (since ASDA is by definition longer than TORA?)