VOA慢速英语:Researchers in South Africa Announce a New Weapon in AIDS Fight

almost, nearly, about, approximately, around, roughly

这些副词均有“大约，差不多”之意

almost ：指在程度上相差很小，差不多。

nearly与almost含义基本相同，侧重指数量、时间或空间上的接近。

about ：常可分almost和nearly换用，但about用于表示时间、数量的“大约”时，实际数量可能多也可能少。

approximately ：多用于书面语，指精确度接近某个标准以致误差可忽略不计。

around ：多用于非正式场合，常见于美国英语。

roughly ：指按精略估计，常代替about。

2.They were advised to use another form of HIV prevention.

advise用法

1)用作及物动词时，注意后接动名词 (不能直接跟不定式)或不定式的复合结构：

正：He advised leaving early. 他建议早点出发。

正：He advised us to leave early. 他建议我们早点出发。

误：He advised to leave early.

注意 advise 后接不定式复合结构时的被动语态形式 (不要与上面第一个句型混为一谈)：

He advised us to leave early. (主动式)

→We were advised to leave early. (被动式)  (from www.nmet168.com)

2)其后若接 that 从句，通常要用虚拟语气 (should＋v. )：

He advised that we (should) leave early. 他建议我们早点出发。

We advised that he should leave early. 我们建议他早点出发。

He advised that everyone should buy one. 他建议每人买一个。

3.Women who used the gel more than eighty percent of the times when they had sex had fifty-four percent fewer HIV infections.

这句话的主干是：Women had fifty-four percent fewer HIV infections。
who used the gel more than是定语从句，修饰Women。when they had sex是时间状语从句。

4.Others say some women may have had sex with infected men who had very high amounts of the virus.

may have had对过去发生的事情表示不确定的猜测。