The child is as good as gold.
　　
（误译）这个孩子像黄金那样宝贵。
（正译）这个孩子很乖。

as good as gold 是习语，虽然有很多as... as... 形式的词组可以直译，例如as... as ever (always) 可直译为“与往常一样......”，但 as good as gold 则有特殊的意义（“很乖”），不能按字面直译。

“乖”的内涵和引申：

1. clever adj. 聪明的；机灵的；熟练的

Even the media occasionally try to trick the public with a clever April Fool story.
大众媒体偶尔也会以巧妙的愚人节故事来愚弄公众。

If such a clever person becomes arrogant or sarcastic, however, their words can hurt you.
如果这样聪明的人变得傲慢和自大，他们就可能会伤害到你。

2. alert vt. 使警觉，使意识到；警告
adj. 警惕的，警觉的；留心的
n. 警报；警戒，警惕

My horse was not above medium size, but he was alert.
我所骑的马，大小不过中等，但是感觉灵敏。

Be alert to students expressing overwhelming feelings in discussions.
警惕学生在陈述时的感情失控。

3. good adj. 好的；优良的；愉快的；虔诚的
n. 好处；善行；慷慨的行为
adv. 好

A good lather is half the shave.
好的泡沫是修面成功的一半。

The news is too good to be true.
那消息太好了，很难相信是真的。

4. perverse 乖张的，倔强的违反常情的

There could be perverse results, too.
这样做确实也可能产生荒唐的结果。

America's health-care system is a nightmare of perverse incentives.
美国的医疗保健系统具有反动力。

5. shrewd adj. 精明的；狡猾的；机灵的
n. 精明（的人）；机灵（的人）

Yet in many respects it was a shrewd move.
然而，在很多方面，荷兰都有着良好的发展。

He was too shrewd to believe that it must exist.
他到是不至于愚蠢到相信那一定会存在。