1 Many sentences in English contain two clauses: a main clause and a "that" clause. The "that" clause contains "that" + S + V. The "that" clause is the object of certain verbs and adjectives. The word "that" is usually optional in these sentences.
2 Verbs that show a person's thoughts or feelings can be followed by a "that" clause. In each of these examples, the subject is a person. The "that" clause explains the subject's thoughts or feelings. Notice that the word "that" is optional.
I think that we should wait for his response.
Are you sure that he will give us better offer?
3 Verbs with that clauses
I think(fell, believe, assmue) that we have a lot of competition.
4 The verb "to be" can also be followed by a "that" clause. In each of these sentences, the subject is a problem, idea, or situation. The "that" clause explains what the problem, idea, or situation is. Notice that the word "that" is optional.
The problem(issue, point, difficulty) is that our sales department is too small.
5 Adjectives with that clauses
Adjectives that show a person's thoughts or feelings can be followed by a "that" clause. With adjectives like "sure," "glad," "sorry," and "worried," the subject in the main clause is a person. The "that" clause explains the person's thoughts and feelings. The word "that" is optional.
She is sure(glad, sorry, worried) that Greg will be promoted.
6 Adjectives that describe a situation
Adjectives that describe a situation can also be followed by a "that" clause. With adjectives such as "true," "strange," "obvious," and "too bad" the subject in the main clause is "it." The "that" clause describes the situation. The word "that" is optional. Remember that "it is" can be shortened to "it's."
It is true(strange, obvious, too bad) that she missed the meeting today.