12. The chimney that was blown down last night in the storm should have been mended long ago.
13. The old ruined tower which has long been a picturesque sight in the village was blown down last night.
14. We counted ten chimneys that were blown down last night.
15. The stenography system that I studied is Munson's.
16. I think she uses Munson's which she considers a good system of stenography.
17. Last year I pursued a course in stenography which I enjoyed very much.
18. The book that we use in class has a brown cover.
19. The only milk that is fit to drink comes from a clean dairy.
20. Systematic inspection has been carried on which has resulted in securing better milk.
Rule 9.—A non-restrictive clause should be separated from the rest of the sentence by commas.