Question

Which sentence contains a nonrestrictive clause?

Be sure to watch that movie I gave you.
The man who drives our bus is ill.
Take a left after that house with the yellow fence.
The old apron, which belonged to Mama, is torn.

Answer 1

"The old apron, which belonged to Mama, is torn."

The clause "which belonged to Mama" is nonrestrictive — it adds extra information and is set off by commas.