既然表语从句中的引导词“that”一般不能省略，为什么下面这句话中省略了？

Question

what matters is we should realize that online dictionaries are only intelligent learning tools used to serve mankind.

Answer 1

回答如下：
连接词that可以引导名词从句(主语从句、宾语从句、表语从句和同位语从句)，它在名词从句中无词义，不作任何成分。that引导主语从句时，若其置于句首，that不能省略; 若其置于主句之后，即前面用it作形式主语时，则that可以省略。例如：
That he is ill is true = It is true (that) he is ill.
that 引导宾语从句时，通常可以省略。但谓语动词与宾语从句之间或者that从句之间有插入词语时，that不能省略; 若动词的宾语是两个以上的that从句，第一个that可以省略，其余的that不能省略; 若that从句前有形式宾语it+宾补，则that不能省略。例如：
He said (that) he was 45.
He told us, for the first time, that he was dismissed by the boss.
He told me that, if he was free, he would come to my help.
He said (that) he was 72 and that his wife was 68.
I feel it a pity that you missed the chance.
that引导表语从句时，通常不能省略。但在非正式英语中有省略现象。另外，前面的主语从句中有行为动词do时，引导表语从句的that可以省略。例如：
What we will do next is (that) we will have more people know the fact.
The truth is (that) he lied to all of us.
that引导同位语从句时，that不能省略。例如：
We know the fact that he is fired.
The news came that he had won the prize.追问

谢谢，补充说明：
语法规定，that 引导主语从句，在句首时不可省略that。当it 作形式主语，在口语和非正式文体中，that 偶尔可以省略，尤其多见于非常短的句子中。不过，为了正确起见，建议最好不要省略。
It’s too bad you can’t come to the party. 你不能来参加宴会真遗憾。

Answer 2

这得看你是在哪里看到这句话的。

is后面的引导词that不能省略，表语从句的引导词。这里省略了是不对的。

在表语从句中，that作引导词时，有省略的情况:

①例如:it作形式主语，会有省略that的现象。

It is a pity (that) you missed the bus yesterday.

②非正式用语中，非正式场合中有时可以省略。

The only problem is (that) you can't eat trees.

本回答被网友采纳

Answer 3

不是不可以省略，一般不能省略，如果表语比较长，尤其是有that引导的从句，就可以省略。

Answer 4

跟你同样迷惑，回应一下表示点赞。
对的，名词性从句中除了宾语从句的引导词that可以省略，其它三个名词性从句的that都不能省略。
这句的表语从句that不能省略。但又被省略了，那就只有问作者本人了，希望他能给个解释。你能联系到作者吗？我也很想知道原因。追问

额，这个好像是《巨微英语》的作文范文里的句子。