He said, "I clean my teeth twice a day."

Answer: Option B

1. Understanding the sentence in direct speech:
The original sentence is: "I clean my teeth twice a day."
Here, "clean" is in the present simple tense, which is used for habitual actions or routines.

2. Identifying the reporting verb:
The reporting verb is "said", which is in the past tense. In indirect speech, the tense of the reporting verb influences whether we backshift (change) the tense in the reported clause.

3. Rules for changing tenses in indirect speech:
Normally, if the reporting verb is in the past tense, we backshift the tense of the reported verb (e.g., present → past).
However, there are exceptions. If the reported statement expresses a universal truth, fact, or a habitual action that is still true, we keep the tense as it is.

4. Applying the rule here:
The statement "I clean my teeth twice a day" describes a habitual action that is still true for the speaker at the time of reporting. Therefore, we do not need to change the verb "clean" to "cleaned".

5. Converting to indirect speech:
Remove the quotation marks.
Change "I" to "he" (as the speaker is referred to in third person).
Keep "clean" in present tense but adjust for third-person singular → "cleans".
The sentence becomes: He said that he cleans his teeth twice a day.

6. Checking other options:
Option A ("cleaned") → Incorrect, because it unnecessarily changes the tense.
Option C ("used to clean") → Incorrect, because it implies the habit is no longer true.
Option D ("is used to cleaning") → Incorrect, because it changes the meaning to showing familiarity with the action, not reporting the statement directly.

Final Answer: Option B is correct because it follows the indirect speech rule for habitual actions that remain true.