Take another look at the sentence:

The computer began to wail like an ambulance, startling poor Robert, who only wanted to retrieve his paper, unfortunately, a virus had immobilized the hard drive.

The computer began to wail like an ambulance is a main clause. Startling poor Robert is a present participle phrase. A present participle phrase will begin with an ing word like startling. When you attach a participle phrase to the end of a main clause, you will frequently need a comma.

Go back to the sentence to try again.

HomeTermsExercises MOOCHandoutsPresentationsVideosRulesAboutShopFeedback