The indefinite pronoun it is often used as the subject of a sentence, and an appositive clause, used to explain the pronoun, is put after the predicate. See Sentence 7, Exercise 160.

129. That is often used merely as an introductory-word in a noun clause; thus, I believe that she will come. Show that the word that is not needed to express the thought of the clause.

Often, however, the word that, when it is the first word in a noun clause, has an important use. Show that it is needed in the following sentence: He said, "That is surely a mistake"

Exercise 161

Show by sentences given in Exercise 160 that the word thai may be either a mere introductory word or a necessary word in a noun clause.