a second-string quarterback的用法和样例：
- He has a second string to his bow.
- I'll just job down that telephone number. We have a baby-sister that can usually come but it does no harm to have a second string.
- A young man who learns two trades has a second string to his bow, so he is unlikely to be out if work for long.
- He had a second string to his bow, so when he lost his job as a toolmaker he became a gardener.
- Wilson was a second string for New Zealand in last week's match.
- He had a second string to his bow,so when he lost his job as a toolmaker he became a gardener.