Spot the non-defining-clause error: the Riverside Theatre is already identified by name. Which revision is standard?
The Riverside Theatre, which they renovated in spring, has reopened.✓Correct answer
The Riverside Theatre, they renovated in spring, has reopened.
The Riverside Theatre which they renovated in spring has reopened.
The Riverside Theatre, that they renovated in spring, has reopened.
Explanation
Which must remain as the object of renovated in this non-defining clause, and the clause stays between commas. The contact-clause version is the closest distractor because object pronouns may be omitted in defining clauses but not in non-defining ones.