Exercise; adding or removing commas. -- The World Bank

[Aikuzo]

Instruction: Edit the following essay by adding or removing commas.

3. The World Bank, which conducted a study in 1997, looked at health-care claim forms that were filled by workers. According to the study, male workers who traveled extensively filed 80 percent more forms than their colleagues, (no comma should be here) who did not travel. My travel companion, for example, suffers from stress-related ailments.

Perfect?
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I quit studying English years ago and have just come back to study the basics.

[Mister Micawber]

OK
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Native English teacher at Mister Micawber's