Which of the following is TRUE according to the passage?
You should cover your mouth and nose with a piece of paper when you sneeze or cough.
Some doctors say that washing your hands can stop the flu as much as 80%.
It's easy to be infected with H7N9 virus, so you mustn't go to the places with groups of people.
Some people who were infected with the H7N9 virus had a toothache.