VOA慢速英语:Fish Farms May Soon Supply More Than Half the World's Catch

no longer不再, 已不, 不复, 再也不

例句：He was long a famous musician, but he plays no longer.
      他成为有名的音乐家已很久了, 但他现在不演奏了。

      The city's water supply is no longer adequate for its need.
      这个城市的供水已不敷需求。

2.The FAO says each person ate an average of almost seventeen kilograms of fish last year.

an average of平均有(跟数词)

例句：An average of ten students are absent each day .
      每天平均有10个学生缺课。

average用作名词，注意以下用法：

(1) 表示“平均”、“平均数”，是可数名词。如：

The average of 6，8 and 10 is 8. 6，8，10的平均数是8。

An average of 10 students are absent each day. 平均每天有10个学生缺席。

It’s said thatthe paper receive an average of nearly 100 articles a day. 据说这个报社平均每天要收到百来篇来稿。

(2) 表示“普通”、“标准”、“平常”等（大致相当于“一般水平”的意思)，根据情况可用作可数或不可数名词。如：

Tom’s work atschool is above (the) average, Jim’s is below (the) averageand Jack’s is up to (the) average. 汤姆的学习成绩属于中上水平，吉姆的学习成绩属中下水平，杰克的学习成绩属中等水平。

(3) 表示“平均起来”、“在一般情况下”，可用 on average, onan (the) average。如：

On (the) average we receive ten letters eachday. 我们平均每天收到10封信。

He smokes 20 cigarettes a dayon an average. 他平均每天要抽20支烟。

3.Some aquaculture critics doubt that aquaculture can keep growing at the current rate.

keep doing的用法

含keep的常用句型

keep doing sth. 意为"继续干某事"，表示不间断地持续干某事，keep后不能接不定式或表示静止状态的v-ing形式，而必须接延续性的动词。如：

He kept working all day, because he wanted to finish the work on time.他整天都在不停地工作，因为他想准时完成工作。

Keep passing the ball to each other, and you'll be OK.坚持互相传球，你们就行。

keep on doing sth. 意为"持续做某事"。如：

The pupil kept on asking me the same question.这个学生不断地问我同一个问题。

I kept on thinking about the match in the afternoon.我总是想起下午的那场比赛。

keep...from doing sth.意为"阻止/防止……做某事"。如：

The heavy snow kept us from going out.大雪使我们不能出去。

4.China produces more than sixty percent of the world’s farmed fish.

more than超过,多于

例句：It's no more than one mile to the shops.
      到商业区不过一英里。

      His insolence is more than I can stand.
      我受不了他的无礼。