講解：

be supposed to do / be sth
(按規定、習慣、安排等)應當,應,該,須:
You're supposed to buy a ticket, but not many people do.
按說應當買票,不過買的人不多。

warm up
(為體育活動或表演)做適應性練習,做準備活動；熱身
The sportsman is warming up,preparing for the game.
運動員在熱身準備比賽。

fit sb / sth in | fit sb / sth in /'into sth
找到時間(見某人、做某事):
I'll try and fit you in after lunch.
我盡量午飯后抽時間見你。

lend (out) sth (to sb) | ~ (sb) sth
借給；借出
I've lent the car to a friend.
我把車借給一位朋友了。

expert (at / in / on sth) | ~ (at / in / on doing sth)
專家；行家；能手:
He's an expert at getting his own way.
他在如何達到自己的目的方面很在行

back off
放棄(采取行動)；退讓:
The government backed off from a confrontation.
政府放棄對抗。

drop out
退學；輟學:
She started a degree but dropped out after only a year.
她在攻讀學位僅一年后就退學了。