【今日主题】

And this morning I would like to share a sentence pattern with you which is: It is essential that S should do. 这个句式表达的意思是：完全有必要做某事/一定要做某事/做某事是必不可少的/做某事极其重要/必须做某事, and so on.

【主题详解】

Let's make a sentence with this sentence pattern. It is essential to this job that you should have some experience. 你做这项工作必须有经验。In this sentence, "essential " means completely necessary or extremely important in a particular situation or for a particular activity. 意为：完全必要的，必不可少的，极其重要的。在此句中it 是形式主语，真实主语为由that引导的主语从句that you should have some experience. 此主语从句中使用了虚拟语气，即其谓语形式是：should + 动词原形。其中should可以省略。To this job是做状语,这里强调的是“这项工作”这个事物，而不是“这个晚会”这个事物，好了，现在我们要强调是“你”，而不是“我”，那怎么改写这个句子呢？It is: It is essential to you that some experience for this job should be had. 好了，大家清楚了在这个句型中it is + adj, + to something ( to somebody ) + that S (should) do. 中的to something 和to somebody的区别了吗？从上面的例句可以知道，含有主语从句的复合句中的主句中的表语也就是形容词是essential, necessary等这样表示“必要”的词语时，主语从句中要使用虚拟语气。

【例句及剖析】

Let's look at more example sentences. 1 It is essential that this mission not fail. 这项任务一定不能失败。注意此句中not fail的由来。这里是主语从句使用了否定式，原句为that this mission should not fail. 那么should是可以省略的，因此就是句中的not fail。 2 It is not essential to happiness that money be owned. 金钱对于幸福并非必不可少。这里想必大家都知道主语从句中be的由来了吧，那就不多说了。

【温故知新】

please translate the following sentences into English with today's sentence pattern in different ways among which a subjective clause must be used.

1 将这两组分开是完全有必要的。

2 我们的生活中诸如水，电，燃气等设施是必不可少的。

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