The Ontario Provincial Government Banned Smoking in Public Places and Workplaces

The Ontario provincial government banned smoking in public places and workplaces in 2004.Dr.Sandy Smokesless used public records to compare the incidence rates of lung cancers before and after 2004 to determine whether the smoking ban helped address the threat smoking poses to the health of Ontarians.What sort of experimental research is this?

A) Factorial design
B) Natural experiment
C) Latin square design
D) Interrupted time series design
E) Field research