Parts of the following sentence have been given as options. One of them may contain an error. Select the part that contains the error from the given options. If you don’t find any error, mark ‘No error’ as your answer.

Q:

The reduced air pressure on airline flights can lessen the amount of oxygen in passengers' blood for twenty-five percent.

• 1
  The reduced air pressure on airline flights
• 2
  No error
• 3
  in passengers' blood for twenty-five percent
• 4
  can lessen the amount of oxygen