The correct answer is B. He said that he cleans his teeth twice a day.
The sentence “He said, ‘I clean my teeth twice a day'” is in the present tense. This means that the speaker is talking about a habit or routine that they do regularly. In this case, the speaker is saying that they brush their teeth twice a day.
Option A is incorrect because it uses the past tense. This would be correct if the speaker was talking about something that they used to do, but they are not.
Option C is incorrect because it uses the past participle “used to.” This would be correct if the speaker was talking about something that they no longer do, but they are not.
Option D is incorrect because it uses the present participle “being used to.” This would be correct if the speaker was talking about something that they are getting used to, but they are not.