384. This is why the number of signals that an animal can make is very limited: the great tit (山雀) is a case in point; it has about twenty different calls, whereas in human language the number of possible utterances is limitless.
譯文
這就是動(dòng)物所能發(fā)出的信號(hào)數(shù)量極為有限的原因：山雀就是個(gè)典型的例子，它有大概20種不同的叫聲，而在人類語(yǔ)言中可能做出的信號(hào)數(shù)量是無(wú)限的。
點(diǎn)睛
this is why...意為“這就是……的原因”。如：
This is why he didn't come. 這就是他沒(méi)來(lái)的原因。
a case in point意為“與所談的事有關(guān)的例證，事例”。如：
As a case in point, let's look at nineteenth-century France. 作為典型的例子，我們來(lái)看看19世紀(jì)的法國(guó)。
whereas此處意為“然而，而”。如：
She earns $10,000 a year whereas he gets at least $100,000. 她一年掙1萬(wàn)美元，而他至少可以掙到10萬(wàn)美元。
考點(diǎn)歸納
this is why...具體說(shuō)明的是結(jié)果，而想要由結(jié)果導(dǎo)出原因，應(yīng)該用the reason why...。如：
The reason why I'm late is that I missed the bus. 我遲到的原因是我沒(méi)趕上公共汽車。
The reason why she didn't come to school is because she got ill. 她沒(méi)來(lái)上學(xué)的原因是她生病了。
