Can that introduce clauses and subject clauses?

That can guide noun clauses and attributive clauses. When that introduces a noun clause (i.e. subject, object, predicate, appositive clause), it has no specific meaning in the clause, but only plays a connecting role, and does not serve as any sentence component in the clause.

In the subject clauses, predicative clauses and appositives introduced by that, that cannot be omitted.

In the object clause introduced by that, that can generally be omitted, but it cannot be omitted in the following situations.

1. In the object clauses after verbs such as suggest and order expressing commands, requests, suggestions, etc., they cannot be omitted.

2. When there are two introductory object clauses connected by and or but, the "that" in the first clause can be omitted, but the "that" in the second clause cannot be omitted.

Analysis:

that, which

Both that and which can introduce attributive clauses, but in the following cases, the relative pronoun that guides attributive clauses can only be used that, not that. which:

1． When the antecedent is an indefinite pronoun such as all, everything, nothing, anything, little, etc., or is modified by words such as first, last, only, few, much, some, any, no, etc., the relative pronoun that should be used instead of which.

2． When the antecedent is modified by the superlative form of an adjective, the relative pronoun is that rather than which.

3. When two parallel antecedents represent people and things respectively, the relative pronoun that should be used instead of which.

4. In the emphatic sentence pattern "It is [was]...that [who]...", only that can be used, not which.