the ones 和the one 的分別..

1. the ones 和the one 的分別

Ｏｎｅ（單）；　Ｏｎｅｓ（複）


Ｈｅ　found his　loved one。他找到他的情人
They foｕnd their loved ones。他們找到他們的情人

2. set out = set off= start journey?

(1) set out:開始
He set out to paint the whole house but finished only the front part.
他開始著手粉刷整幢房子,可是只完成了前面的部分。
（２）set off：出發,動身
They set off in search of the lost child.
他們出發尋找失蹤的孩子。


3. the population will eventually increase to around eight million.


The population of the city ｗｉｌｌ　rise　 to five million.
該市人口將增加到五百萬。

1.
The ones = 眾多的人
The ones who left are the lucky ones. 離開了的是幸運的一群。
The one = 某一個人
The one who knows your name. 那個知到你名字的人。

2.
Set out 和 set off分別有數個解釋。然而，它們也帶有「啟程」或「開始出發」之意思（分別見下面第五項）。
Set Out
I. To begin an earnest attempt; undertake: He set out to understand why the plan had failed.
II. To lay out systematically or graphically: set out a terrace.
III. To display for exhibition or sale.
IV. To plant: set out seedlings.
V. To start a journey: She set out at dawn for town
Set Off
I a. To give rise to; cause to occur: set off a chemical reaction.
I b. To cause to explode: set off a bomb.
I c. To make suddenly or demonstrably angry: The clerk's indifference finally set me off.
II. To indicate as being different; distinguish: features setting him off from the crowd.
III. To direct attention to by contrast; accentuate: set off a passage with italics.
IV. To counterbalance, counteract, or compensate for: Our dismay at her leaving was set off by our knowing that she was happy.
V. To start on a journey: set off for Europe.

3.
你的句子正確。也可考慮這句：
The population will reach some eight million eventually.