备用reserve; spare; replacement; alternate;standby;backup（美）
你在那儿看见的那架巨型喷气机一定是总统的（波音）707～座机。The jumbojet you saw there must be the Presidential backup 707./～方案alternate scheme (or proposal)/～机器standby machine/～金reserve fund/～款项reserve fund/～轮胎spare tyre |