back-up spring

例句：

1. 1. Thecar's back-up spring broke, so we had to drive the restof the way.
   车的备用弹簧坏了，所以我们不得不开剩下的路。
2. 2. The oldhouse needed a new back-up spring to fix itsbroken door.
   这所老房子需要一个新的备用弹簧来修理它的门。
3. 3. The engineerreplaced the back-up spring with astronger one to prevent any further damage.
   工程师用一个更强壮的备用弹簧替换了原来的，以防止任何进一步的损害。