If a father can do a job as fast as his two sons working together, and one son takes 3 hours while the other takes 6 hours to do the job, how many hours will the father take to do the job alone?

• A. 1 hour
• B. 2 hours
• C. 3 hours
• D. 4 hours

• 2 hours

Please select one of the options to reveal the correct answer.