|Which is correct?
Companies have been pressuring the Chinese government for years to crack down on the piracy of movies, _____________.
This one is controversial. The rule is that to avoid confusion when a sentence has a series of three or more words (or word groups), the writer should use commas to separate items in the series. The big question is “should you use a comma before the word and at the end of the series?”
If you agree that the comma stands in for the word “and” — then the answer is no. You wouldn’t say “Companies have been pressuring the Chinese government for years to crack down on the piracy of movies and music and and computer software.”