Answer: “When I brush, I feel pain and my gums bleed.”
Explanation: If he says “My teeth hurt sometimes.” the dentist will not be able to understand when exactly his teeth hurt, it will make it more difficult to get a diagnosis of the problem. “My toothbrush is too hard.” the dentist will just tell him to get a softer one. “My teeth feel fine most of the time.” the dentist will assume that nothing is wrong with his so he will not get help. “When I brush, I feel pain and my gums bleed.” is the best answer because it is honest, the dentist will know when and where the pain occurs, this will also lead to a diagnosis, and the best help.
