Language points
1.In Ghana, India and Singapore, English isused as a working language ..
注意used后面所接的介词，be used for表示用于某种目的，be used as表示“用作..…”。Hemp(大麻)can be used for cloth and ropes.Dustbins are used for household waste.
A red lamp is used as a danger signal.It can be used as an adjective.

2.English is now used by nearly a quarter ofthe world's population, ...
quarter n.四分之一
Only a quarter of the earth is land.Three quarters of the theatre was full.A quarter of the residents are over 55 yearsold.

quarter的基本意思是“四分之一,四等分”,可以用来指距离、数量、价格及物体的四分之一的量,也可专指时间的“一刻钟,十五分钟”或“一季度,三个月”。
It's a quarter past ten.
The flight was put off about a quarterbecause of ground fog.
He pays his rent at the end of each quarter.