reserve; spare; replacement; alternate;standby;backup（美） 你在那兒看見(jiàn)的那架巨型噴氣機(jī)一定是總統(tǒng)的（波音）707～座機(jī)。The jumbojet you saw there must be the Presidential backup 707./～方案alternate scheme (or proposal)/～機(jī)器standby machine/～金reserve fund/～款項(xiàng)reserve fund/～輪胎spare tyre