I.on [美 ɑn, ɔn, 英 ɒn]介词on often appears as the second element of certain verb structures in English (count on, lay on, sign on, etc). For translations, see the relevant verb entry (count, lay, sign, etc).
At the last chance workout, the trainers stress the fact that everyone is weighing in individually, and there is no one left to fall back on if they struggle.
Sand always said that her education was the most important thing to her, stating if her music career was to fail, she would have her education to fall back on.