time is running out before they will have to retreat to the south.被迫向南遷徙的日子正在一步步逼近

run out:用盡；耗盡；期滿

The lease on our flat runs out in a few months.

我們公寓的租約還有幾個(gè)月就到期了。

My passport has run out.

我的護(hù)照已失效。

retreat:撤退；改變；退避

The soldiers had to retreat when they were beaten in battle.

士兵們在戰(zhàn)斗中受挫，不得不撤退。

You can't retreat from the responsibility in this affair.

你不能回避在這一事件中的責(zé)任。

常用短語:

retreat from (v.+prep.)
1.從…撤退move back from a position or danger

The defeated army had to retreat hastily from the field of battle.

敗軍被迫倉皇地從戰(zhàn)場上撤退。

2.避開…move away from or try to get rid of sb/sth

You cannot retreat from your responsibility in this affair.

你不能回避在這一事件中的責(zé)任。

red and yellow pigments build up in their leaves.紅色素和黃色素染上了葉子

build up:逐步增長；積累

The company has built up a large fund for ages.

多年來這個(gè)公司已積累了大量資金。