Non-defining-clause classification: select all statements that are true.
They can add information about an already named person.✓Respuesta correcta
They allow that immediately after the opening comma.
An embedded clause is normally enclosed by commas.✓Respuesta correcta
Their object relative pronoun may always be omitted.
Explicación
These clauses add information about a referent already identified, and an embedded one is normally set off with commas. The omission claim is the closest false statement because even an object relative element must remain in a non-defining clause.