The relative pronoun that always introduces essential information and can be omitted if it is the object of the clause. Relative pronouns CANNOT be omitted when they are the subject of the clause; ...

Relative pronouns close relative pronounA relative pronoun is a word used to link two parts of a sentence together when referring back to something mentioned at the start. are used to link phrases ...

Relative pronouns close relative pronounA relative pronoun is a word used to link two parts of a sentence together when referring back to something mentioned at the start. are used to link phrases ...